Electrode assembly, battery, and battery pack and vehicle including the same

ABSTRACT

An electrode assembly includes a first electrode; a second electrode; and a separator, the first electrode, the second electrode, and the separator wound about an axis defining a core and an outer circumference of the electrode assembly. The first electrode has a pair of first sides and a pair of second sides, a first portion extending between the pair of first sides, and a second portion extending between the pair of first sides, the first portion being coated with an active material, and at least a part of the second portion includes an electrode tab. The second portion includes a first part adjacent to the core of the electrode assembly, a second part adjacent to the outer circumference of the electrode assembly, and a third part between the first part and the second part. The first or second part has a smaller height than the third part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.17/665,896, filed on Feb. 7, 2022, which claims the benefit under 35U.S.C. § 119(a) to Patent Application No. 10-2021-0022881, filed in theRepublic of Korea on Feb. 19, 2021, Patent Application No.10-2021-0022891, filed in the Republic of Korea on Feb. 19, 2021, PatentApplication No. 10-2021-0022894, filed in the Republic of Korea on Feb.19, 2021, Patent Application No. 10-2021-0022897, filed in the Republicof Korea on Feb. 19, 2021, Patent Application No. 10-2021-0024424, filedin the Republic of Korea on Feb. 23, 2021, Patent Application No.10-2021-0030291, filed in the Republic of Korea on Mar. 8, 2021, PatentApplication No. 10-2021-0030300, filed in the Republic of Korea on Mar.8, 2021, Patent Application No. 10-2021-0046798, filed in the Republicof Korea on Apr. 9, 2021, Patent Application No. 10-2021-0058183, filedin the Republic of Korea on May 4, 2021, Patent Application No.10-2021-0077046, filed in the Republic of Korea on Jun. 14, 2021, PatentApplication No. 10-2021-0084326, filed in the Republic of Korea on Jun.28, 2021, Patent Application No. 10-2021-0131205, filed in the Republicof Korea on Oct. 1, 2021, Patent Application No. 10-2021-0131207, filedin the Republic of Korea on Oct. 1, 2021, Patent Application No.10-2021-0131208, filed in the Republic of Korea on Oct. 1, 2021, PatentApplication No. 10-2021-0131215, filed in the Republic of Korea on Oct.1, 2021, Patent Application No. 10-2021-0131225, filed in the Republicof Korea on Oct. 1, 2021, Patent Application No. 10-2021-0137001, filedin the Republic of Korea on Oct. 14, 2021, Patent Application No.10-2021-0137856, filed in the Republic of Korea on Oct. 15, 2021, PatentApplication No. 10-2021-0142196, filed in the Republic of Korea on Oct.22, 2021, Patent Application No. 10-2021-0153472, filed in the Republicof Korea on Nov. 9, 2021, Patent Application No. 10-2021-0160823, filedin the Republic of Korea on Nov. 19, 2021, Patent Application No.10-2021-0163809, filed in the Republic of Korea on Nov. 24, 2021, PatentApplication No. 10-2021-0165866, filed in the Republic of Korea on Nov.26, 2021, Patent Application No. 10-2021-0172446, filed in the Republicof Korea on Dec. 3, 2021, Patent Application No. 10-2021-0177091, filedin the Republic of Korea on Dec. 10, 2021, Patent Application No.10-2021-0194572, filed in the Republic of Korea on Dec. 31, 2021, PatentApplication No. 10-2021-0194593, filed in the Republic of Korea on Dec.31, 2021, Patent Application No. 10-2021-0194610, filed in the Republicof Korea on Dec. 31, 2021, Patent Application No. 10-2021-0194611, filedin the Republic of Korea on Dec. 31, 2021, Patent Application No.10-2021-0194612, filed in the Republic of Korea on Dec. 31, 2021, andPatent Application No. 10-2022-0001802, filed in the Republic of Koreaon Jan. 5, 2022, all of these applications being hereby expressly andfully incorporated by reference in their entireties into the presentapplication.

Also, Patent Application No. 10-2021-0007278, filed in the Republic ofKorea on Jan. 19, 2021, is hereby expressly incorporated by reference inits entirety into the present application.

TECHNICAL FIELD

The present disclosure relates to an electrode assembly, a battery, anda battery pack and a vehicle including the same.

BACKGROUND ART

Secondary batteries that are easily applicable to various product groupsand have electrical characteristics such as high energy density areuniversally applied not only to portable devices but also to electricvehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electricdrive source.

These secondary batteries are attracting attention as a new energysource to improve eco-friendliness and energy efficiency because theyhave the primary advantage that they can dramatically reduce the use offossil fuels as well as the secondary advantage that no by-products aregenerated from the use of energy.

Secondary batteries currently widely used in the art include lithium ionbatteries, lithium polymer batteries, nickel cadmium batteries, nickelhydrogen batteries, nickel zinc batteries, and the like. A unitsecondary battery, namely a unit battery, has an operating voltage ofabout 2.5V to 4.5V. Therefore, when a higher output voltage is required,a battery pack may be configured by connecting a plurality of batteriesin series. In addition, a plurality of batteries may be connected inparallel to form a battery pack according to the charge/dischargecapacity required for the battery pack. Accordingly, the number ofbatteries included in the battery pack and the form of electricalconnection may be variously set according to the required output voltageand/or charge/discharge capacity.

Meanwhile, as a kind of unit secondary battery, there are knowncylindrical, rectangular, and pouch-type batteries. In the case of acylindrical battery, a separator serving as an insulator is interposedbetween a positive electrode and a negative electrode, and they arewound to form an electrode assembly in the form of a jelly roll, whichis inserted into a battery housing to configure a battery. In addition,a strip-shaped electrode tab may be connected to an uncoated portion ofeach of the positive electrode and the negative electrode, and theelectrode tab electrically connects the electrode assembly and anelectrode terminal exposed to the outside. For reference, the positiveelectrode terminal is a cap of a sealing body that seals the opening ofthe battery housing, and the negative electrode terminal is the batteryhousing. However, according to the conventional cylindrical batteryhaving such a structure, since current is concentrated in thestrip-shaped electrode tab coupled to the uncoated portion of thepositive electrode and/or the uncoated portion of the negativeelectrode, the current collection efficiency is not good due to largeresistance and large heat generation.

For small cylindrical batteries with a form factor of 1865 (diameter: 18mm, height: 65 mm) or 2170 (diameter: 21 mm, height: 70 mm), resistanceand heat are not a major issue. However, when the form factor isincreased to apply the cylindrical battery to an electric vehicle, thecylindrical battery may ignite while a lot of heat is generated aroundthe electrode tab during the rapid charging process.

In order to solve this problem, there is provided a cylindrical battery(so-called tab-less cylindrical battery) in which the uncoated portionof the positive electrode and the uncoated portion of the negativeelectrode are designed to be positioned at the top and bottom of thejelly-roll type electrode assembly, respectively, and the currentcollector is welded to the uncoated portion to improve the currentcollecting efficiency.

FIGS. 1 to 3 are diagrams showing a process of manufacturing a tab-lesscylindrical battery. FIG. 1 shows the structure of an electrode, FIG. 2shows a process of winding the electrode, and FIG. 3 shows a process ofwelding a current collector to a bent surface region of an uncoatedportion.

Referring to FIGS. 1 to 3 , a positive electrode 10 and a negativeelectrode 11 have a structure in which a sheet-shaped current collector20 is coated with an active material 21, and include an uncoated portion22 at one long side along the winding direction X. The long side is adirection parallel to the x-axis direction and means a side with arelatively long length.

An electrode assembly A is manufactured by sequentially stacking thepositive electrode and the negative electrode 11 together with twosheets of separators 12 as shown in FIG. 2 and then winding them in onedirection X. At this time, the uncoated portions of the positiveelectrode 10 and the negative electrode 11 are arranged in oppositedirections.

After the winding process, the uncoated portion 10 a of the positiveelectrode 10 and the uncoated portion 11 a of the negative electrode 11are bent toward the core. After that, current collectors 30, 31 arewelded and coupled to the uncoated portions 10 a, 11 a, respectively.

An electrode tab is not separately coupled to the positive electrodeuncoated portion 10 a and the negative electrode uncoated portion 11 a,the current collectors 30, 31 are connected to external electrodeterminals, and a current path is formed with a large cross-sectionalarea along the winding axis direction of electrode assembly A (seearrow), which has an advantage of lowering the resistance of thebattery. This is because resistance is inversely proportional to thecross-sectional area of the path through which the current flows.

In the tab-less cylindrical battery, in order to improve the weldingcharacteristics of the uncoated portions 10 a, 11 a and the currentcollectors 30, 31, a strong pressure should be applied to the weldingregion of the uncoated portions 10 a, 11 a to bend the uncoated portions10 a, 11 a as flat as possible.

However, when the welding region of the uncoated portions 10 a, 11 a isbent, the shapes of the uncoated portions 10 a, 11 a may be irregularlydistorted and deformed. In this case, the deformed portion may come intocontact with the electrode of opposite polarity to cause an internalshort circuit or cause micro cracks in the uncoated portions 10 a, 11 a.In addition, as the uncoated portion 32 adjacent to the core of theelectrode assembly A is bent, all or a significant portion of the cavity33 in the core of the electrode assembly A is blocked. In this case, itcauses a problem in the electrolyte injection process. That is, thecavity 33 in the core of the electrode assembly A is used as a passagethrough which an electrolyte is injected. However, if the correspondingpassage is blocked, electrolyte injection is difficult. In addition,while an electrolyte injector is being inserted into the cavity 33, theelectrolyte injector may interfere with the uncoated portion 32 near thecore, which may cause the uncoated portion 32 to tear.

In addition, the bent portions of the uncoated portions 10 a, 11 a towhich the current collectors 30, 31 are welded should be overlapped inmultiple layers and there should not be any empty spaces (gaps). In thisway, sufficient welding strength may be obtained, and even with thelatest technology such as laser welding, it is possible to prevent laserfrom penetrating into the electrode assembly A and melting the separatoror the active material.

Meanwhile, in the conventional tab-less cylindrical battery, thepositive electrode uncoated portion 10 a is formed entirely on the upperportion of the electrode assembly A. Therefore, when the outercircumference of the top of the battery housing is pressed inward toform a beading portion, a top edge area 34 of the electrode assembly Ais compressed by the battery housing. This compression may cause apartial deformation of the electrode assembly A, which may tear theseparator 12 and cause an internal short circuit. If a short circuitoccurs inside the battery, it may cause heating or explosion of thebattery.

SUMMARY OF THE DISCLOSURE Technical Problem

The present disclosure is designed to solve the problems of the relatedart, and therefore the present disclosure is directed to providing anelectrode assembly having an improved uncoated portion structure torelieve stress applied to the uncoated portion when bending the uncoatedportion exposed at both ends of the electrode assembly

The present disclosure is also directed to providing an electrodeassembly in which an electrolyte injection passage is not blocked evenif the uncoated portion is bent.

The present disclosure is also directed to providing an electrodeassembly including a structure that may prevent a top edge of theelectrode assembly from contacting an inner surface of a battery housingwhen the top of the battery housing is beaded.

The present disclosure is also directed to providing an electrodeassembly with improved physical properties of a welding region byapplying a segment structure to the uncoated portion of the electrodeand optimizing the dimensions (width, height, separation pitch) of thesegments to sufficiently increase the number of overlapping layers ofthe segments in an area used as a welding target region.

The present disclosure is also directed to providing an electrodeassembly with improved energy density and reduced resistance by applyinga structure in which a current collector is welded over a large area toa bending surface region formed by bending the segments.

The present disclosure is also directed to providing a battery includinga terminal and a current collector having an improved design so as toperform electrical wiring at an upper portion thereof.

The present disclosure is also directed to providing a battery includingthe electrode assembly having an improved structure, a battery packincluding the battery, and a vehicle including the battery pack.

The technical objects to be solved by the present disclosure are notlimited to the above, and other objects not mentioned herein will beclearly understood by those skilled in the art from the followingdisclosure.

Technical Solution

In one aspect of the present disclosure, there is provided an electrodeassembly including a first electrode; a second electrode; and aseparator between the first electrode and the second electrode, thefirst electrode, the second electrode, and the separator wound about anaxis defining a core and an outer circumference of the electrodeassembly, wherein the first electrode has a pair of first sides and apair of second sides extending between the pair of first sides, a firstportion extending between the pair of first sides, and a second portionextending between the pair of first sides, wherein the first portion iscoated with an active material along a winding direction, and at least apart of the second portion includes an electrode tab, wherein the secondportion includes a first part adjacent to the core of the electrodeassembly, a second part adjacent to the outer circumference of theelectrode assembly, and a third part between the first part and thesecond part, and wherein the first part or the second part has a smallerheight than the third part in a direction of the axis.

The third part may be bent along a radial direction of the electrodeassembly to be the electrode tab.

The second part and the third part may be bent along a radial directionof the electrode assembly to define the electrode tab.

At least a partial region of the third part is divided into a pluralityof segments that are independently bendable.

Each of the plurality of segments may have a geometric shape in whichone or more straight lines, one or more curves, or a combination thereofare connected.

In each of the plurality of segments, a width of a lower portion may begreater than a width of an upper portion.

In each of the plurality of segments, a width of a lower portion may beidentical to a width of an upper portion.

Each of the plurality of segments may have a width that graduallydecreases from a lower portion to an upper portion.

Each of the plurality of segments may have a width that graduallydecreases and then increases from a lower portion to an upper portion.

Each of the plurality of segments may have a width that graduallyincreases and then decreases from a lower portion to an upper portion.

Each of the plurality of segments may have a width that graduallyincreases and then is kept constant from a lower portion to an upperportion.

Each of the plurality of segments may have a width that graduallydecreases and then is kept constant from a lower portion to an upperportion.

The plurality of segments may have a lower internal angle that increasesindividually or in groups in one direction parallel to the windingdirection.

The lower internal angle of the plurality of segments may increaseindividually or in groups in the range of 60 to 85 degrees in the onedirection parallel to the winding direction.

Each of the plurality of segments may have a geometric shape with awidth that gradually decreases from a lower portion to an upper portion,and a lower internal angle (θ) of a segment located in a winding turnhaving a radius r based on the core of the electrode assembly fallswithin an angle range of the following formula:

${\cos^{- 1}( \frac{0.5*D}{r} )} \leq \theta \leq {\tan^{- 1}( \frac{2*H*\tan\theta_{refer}}{{2*H} - {p*\tan\theta_{refer}}} )}$

wherein D is a width of the segment in the winding direction, r is aradius of the winding turn including the segment, H is a height of thesegment, and p is a separation pitch of the segment.

Each of the plurality of segments may have a side formed with one ormore straight lines, one or more curves, or a combination thereof.

Each of the plurality of segments may have a side that is convex outwardor convex inward.

A corner of an upper portion of each of the plurality of segments mayhave a round shape.

The plurality of segments may have a cut groove between segmentsadjacent to each other along the winding direction, and a lower portionof the cut groove may include a bottom portion and a round portionconnecting both ends of the bottom portion to sides of the segmentsadjacent to each other.

The round portion of the cut groove may have a radius of curvaturegreater than 0 and equal to or smaller than 0.1 mm.

The round portion of the cut groove may have a radius of curvature of0.01 mm to 0.05 mm.

The bottom portion of the cut groove may be flat.

A separation pitch defined as an interval between two points at whichlines extending from the sides of two segments located at both sides ofthe cut groove meet a line extending from the bottom portion of the cutgroove may be 0.05 mm to 1.00 mm.

The plurality of segments may be made of an aluminum foil, and aseparation pitch defined as an interval between two points at whichlines extending from the sides of two segments located at both sides ofthe cut groove meet a line extending from the bottom portion of the cutgroove may be 0.05 mm to 1.00 mm.

The bottom portion of the cut groove may be spaced apart from the firstportion by a predetermined distance.

The predetermined distance may be 0.2 mm to 4 mm.

A bending region of the plurality of segments in a radial direction ofthe electrode assembly may be located in the range of 0 to 1 mm above alower end of the cut groove.

In each of the plurality of segments, a circumferential angle of an arcformed by a lower end of the segment based on a core center of theelectrode assembly may be 45 degrees or less. In each of the pluralityof segments, a width of the segment in the winding direction D(r) maysatisfy the following formula:

1≤D(r)≤(2*π*r/360°)*45°,

wherein r is a radius of a winding turn including the segment based on acore center of the electrode assembly.

In each of the plurality of segments, as the radius r of the windingturn where the segment is located based on the core center of theelectrode assembly increases, the width D(r) in the winding directionmay increase or decrease gradually or stepwise.

In each of the plurality of segments, as the radius r of the windingturn where the segment is located based on the core center of theelectrode assembly increases, the width D(r) in the winding directionincreases gradually or stepwise and then decreases gradually or stepwiseor decreases gradually or stepwise and then increases gradually orstepwise.

In the plurality of segments, the circumferential angle may besubstantially the same based on the core center of the electrodeassembly.

Widths of the plurality of segments in the winding direction mayincrease at substantially the same rate along one direction parallel tothe winding direction of the electrode assembly.

In each of the plurality of segments, as a radius r of the winding turnwhere the segment is located based on the core center of the electrodeassembly increases, a width in the winding direction may increasegradually or stepwise within the range of 1 mm to 11 mm.

In at least a partial region of the third part, a height in thedirection of the axis may change gradually or stepwise along onedirection parallel to the winding direction.

In at least a partial region of the second part and the third part, aheight in the direction of the axis may change gradually or stepwisealong one direction parallel to the winding direction.

The third part may be divided into a plurality of regions havingdifferent heights along one direction parallel to the winding direction,and the height of the third part in the plurality of regions mayincrease gradually or stepwise along one direction parallel to thewinding direction. The second portion may include a height variableregion in which a height of the segment increases stepwise from a firstheight h₁ to an N−1^(th) height h_(N-1), and a height uniform region inwhich the height of the segment is maintained as an N^(th) height h_(N)which is greater than h_(N-1), and N is a height index and a naturalnumber of 2 or above.

N may be a natural number of 2 to 30.

A plurality of segments may have a height h_(k), and the plurality ofsegments having the height h_(k) may be disposed in at least one windingturn, and k is a natural number of 1 to N.

The core of the electrode assembly may not be covered by a bent portionof the segment located at r_(k) by at least 90% or more of a diameterthereof, wherein r_(k) is a start radius of a winding turn including thesegment having a height h_(k), and k is a natural number of 1 to N.

A height h_(k) of the segment may satisfy the following formula:

2 mm≤h_(k)≤r_(k)−α*r_(c)

wherein r_(k) is a start radius of a winding turn including the segmenthaving a height h_(k), k is a natural number of 1 to N, r_(c) is aradius of the core, and a is 0.90 to 1.

The electrode assembly may include a segment skip region having nosegment, a height variable region where segments have variable heights,and a height uniform region where segments have a substantially uniformheight in order along a radial direction, based on a cross section alongthe direction of the axis, and the plurality of segments may be disposedin the height variable region and the height uniform region and bentalong the radial direction of the electrode assembly forming a bendingsurface region.

The first part may not be divided into segments, and the segment skipregion may correspond to the first part.

The third part may be divided into a plurality of segments that areindependently bendable, and the height variable region and the heightuniform region may correspond to the third part.

The second part and the third part may be divided into a plurality ofsegments that are independently bendable, and the height variable regionand the height uniform region may correspond to the second part and thethird part.

In the height variable region and the height uniform region, a maximumheight h_(max) of the segments may satisfy the following formula:

h_(max)≤W_(foil)−W_(scrap,min)−W_(margin,min)−W_(gap)

wherein W_(foil) is a width of a current collector foil before segmentsare formed, W_(scrap,min) is a width corresponding to a minimum cutscrap margin when segments are formed by cutting the current collectorfoil, W_(margin,min) is a width corresponding to a minimum meanderingmargin of the separator, and W_(gap) is a width corresponding to aninsulation gap between an end of the separator and an end of the secondelectrode facing the first electrode with the separator therebetween.

The first electrode may be a positive electrode and the insulation gapmay be in the range of 0.2 mm to 6 mm.

The first electrode may be a negative electrode and the insulation gapmay be in the range of 0.1 mm to 2 mm.

The minimum cut scrap margin may be in the range of 1.5 mm to 8 mm.

The minimum meandering margin may be in the range of 0 to 1 mm.

The minimum cut scrap margin may be zero.

The heights of the segments disposed in the height variable region mayincrease gradually or stepwise within the range of 2 mm to 10 mm.

A ratio of a radial length of the segment skip region to a radius of theelectrode assembly except for the core in the radial direction of theelectrode assembly may be 10% to 40%.

A ratio of a radial length of the height variable region to a radiallength corresponding to the height variable region and the heightuniform region in the radial direction of the electrode assembly may be1% to 50%.

A ratio of a length of an electrode area corresponding to the segmentskip region to the entire length of the first electrode may be 1% to30%.

A ratio of a length of an electrode area corresponding to the heightvariable region to the entire length of the first electrode may be 1% to40%.

A ratio of a length of an electrode area corresponding to the heightuniform region to the entire length of the first electrode may be 50% to90%.

Widths of the plurality of segments in the winding direction or heightsthereof in the direction of the axis, or both may increase gradually orstepwise along one direction parallel to the winding direction.

Widths of the plurality of segments in the winding direction or heightsthereof in the direction of the axis, or both may increase gradually orstepwise and then may decrease gradually or stepwise along one directionparallel to the winding direction or may decrease gradually or stepwiseand then may increase gradually or stepwise along the one directionparallel to the winding direction.

The plurality of segments may form a plurality of segment groups alongone direction parallel to the winding direction of the electrodeassembly, and segments belonging to the same segment group may besubstantially the same as each other in terms of a width in the windingdirection and a height in the direction of the axis.

Widths of the segments belonging to the same segment group in thewinding direction or heights thereof in the direction of the axis, orboth may increase stepwise along one direction parallel to the windingdirection of the electrode assembly.

The plurality of segment groups include a combination of segment groupsin which W3/W2 is smaller than W2/W1, and wherein W1, W2 and W3 arewidths in the winding direction of three segment groups successivelyadjacent to each other in one direction parallel to the windingdirection of the electrode assembly, respectively.

The first part may not be divided into segments, and the first part maynot be bent along a radial direction of the electrode assembly.

The second part may not be divided into segments, and the second partmay not be bent along a radial direction of the electrode assembly.

An insulating coating layer may be formed at a boundary between thefirst portion and a region of the second portion provided in a sectionwhere the bottom portion of the cut groove and the first portion areseparated.

The insulating coating layer may include a polymer resin and aninorganic filler dispersed in the polymer resin.

The insulating coating layer may be formed to cover a boundary portionof the first portion and the second portion along the winding direction.

The insulating coating layer may be formed to cover the boundary portionof the first portion and the second portion along the direction of theaxis by a width of 0.3 mm to 5 mm.

An end of the insulating coating layer may be located within the rangeof −2 mm to 2 mm along the direction of the axis with respect to an endof the separator.

The insulating coating layer may be exposed beyond the separator.

A lower end of the cut groove and the insulating coating layer may bespaced apart by a distance of 0.5 mm to 2 mm.

An end of the insulating coating layer in the direction of the axis maybe located within the range of −2 mm to +2 mm based on the lower end ofthe cut groove.

The second electrode may include a third portion coated with an activematerial along the winding direction, and an end of the third portionmay be located between an upper end and a lower end of the insulatingcoating layer in the direction of the axis.

At least one of the third part or the second part may be divided into aplurality of segments that are independently bendable, and the electrodeassembly may include a bending surface region formed by bending theplurality of segments along a radial direction of the electrodeassembly.

When the number of segments meeting a virtual line parallel to thedirection of the axis at any radial location of the bending surfaceregion based on a core center of the electrode assembly is defined asthe number of overlapping layers of segments at the corresponding radiallocation, the bending surface region may include an overlapping layernumber uniform region in which the number of overlapping layers ofsegments is substantially uniform from the core toward the outercircumference and an overlapping layer number decreasing region locatedadjacent to the overlapping layer number uniform region and the numberof overlapping layers of segments in the overlapping layer numberdecreasing region gradually decreases toward the outer circumference.

A radial length of the overlapping layer number uniform region and theoverlapping layer number decreasing region based on the core center ofthe electrode assembly may correspond to a radial length of a radialregion in which winding turns including the plurality of segments arelocated.

The electrode assembly may include a segment skip region having nosegment, a height variable region where segments have variable heights,and a height uniform region where segments have a substantially uniformheight in order along the radial direction, and a radius at which theoverlapping layer number uniform region starts based on the core centerof the electrode assembly may correspond to a radius at which the heightvariable region starts.

In the overlapping layer number uniform region, the number ofoverlapping layers of the segments may be 10 to 35.

The first electrode may be a positive electrode, and in the overlappinglayer number uniform region, an overlapping thickness of segments may bebetween 100 μm and 875 μm.

The first electrode may be a negative electrode, and in the overlappinglayer number uniform region, an overlapping thickness of segments may bebetween 50 μm and 700 μm.

A ratio of a radial length of the overlapping layer number uniformregion to a radial length of the overlapping layer number uniform regionand the overlapping layer number decreasing region may be 30% to 85%.

The electrode assembly may further include a current collector welded tothe bending surface region, and in the radial direction of the electrodeassembly, a welding region of the current collector may overlap with theoverlapping layer number uniform region by at least 50%.

In the radial direction of the electrode assembly, a region of thewelding region of the current collector not overlapping with theoverlapping layer number uniform region may overlap with the overlappinglayer number decreasing region.

An edge of the current collector may be disposed on the bending surfaceregion to cover an end of a bent portion of the outermost segment in theradial direction of the electrode assembly and welded to the bendingsurface region.

A welding strength of the current collector to the welding region may beat least 2 kgf/cm² or more.

A welding strength of the current collector to the welding region may beat least 4 kgf/cm² or more.

The second portion may be made of a metal foil, and the metal foil mayhave an elongation of 1.5% to 3.0% and a tensile strength of 25 kgf/mm²to 35 kgf/mm².

The metal foil may be an aluminum foil.

The first electrode may have a camber length smaller than 20 mm.

In the first portion, a ratio of a length of a short side parallel tothe direction of the axis to a length of a long side parallel to thewinding direction may be 1% to 4%.

A height of the second part may decrease gradually or stepwise from thecore toward the outer circumference of the electrode assembly.

The second part and the third part may be divided into a plurality ofsegments that are independently bendable, and a width in the windingdirection or a height in the direction of the axis of the segmentsincluded in the second part, or both may be greater than those of thesegments included in the third part.

The third part may include a segment skip region having no segment alongone direction parallel to the winding direction.

The third part may include a plurality of segment skip regions along theone direction parallel to the winding direction.

The plurality of segment skip regions may have widths graduallyincreasing or decreasing along the one direction parallel to the windingdirection.

A height of the second portion of the segment skip region may besubstantially the same as a height of the first part or the second part.

The plurality of segments may be located within a circumferential anglerange preset based on a core center of the electrode assembly.

The plurality of segments may be located in at least two sectoralregions or polygonal regions disposed in a circumferential directionbased on a core center of the electrode assembly.

The sectoral region may have a circumferential angle of 20 degrees ormore.

The second electrode may have a pair of third sides and a pair of fourthsides extending between the pair of third sides, a third portionextending between the pair of third sides, and a fourth portionextending between the pair of third sides, the third portion may becoated with an active material along the winding direction and at leasta part of the fourth portion includes an electrode tab, and the fourthportion may include a region divided into a plurality of segments thatare independently bendable, and the plurality of segments may be bentalong a radial direction of the electrode assembly to form a bendingsurface region.

In another aspect of the disclosure, there is also provided an electrodeassembly including a first electrode; a second electrode; and aseparator between the first electrode and the second electrode, thefirst electrode, the second electrode, and the separator wound about anaxis defining a core and an outer circumference of the electrodeassembly, wherein the first electrode has a pair of first sides and apair of second sides extending between the pair of first sides, a firstportion extending between the pair of first sides, and a second portionextending between the pair of first sides, wherein the first portion iscoated with an active material along a winding direction, wherein thesecond portion includes a region divided into a plurality of segmentsthat are independently bendable from the core toward the outercircumference of the electrode assembly, wherein the plurality ofsegments are bent along a radial direction of the electrode assembly toform a bending surface region, and wherein the bending surface regionincludes an overlapping layer number uniform region in which the numberof overlapping layers of the segments is 10 or more and an overlappinglayer number decreasing region located adjacent to the overlapping layernumber uniform region and the number of overlapping layers of thesegments in the overlapping layer number decreasing region decreasesaway from the overlapping layer number uniform region, along the radialdirection.

The electrode assembly may include a segment skip region having nosegment, a height variable region where segments have heights increasingstepwise, and a height uniform region where segments have asubstantially uniform height in order along the radial direction of theelectrode assembly, and a start radius of the overlapping layer numberuniform region may correspond to a start radius of the height variableregion based on a core center of the electrode assembly.

A region of the second portion adjacent to the core may not be dividedinto segments and may be disposed in a winding turn of the segment skipregion.

A ratio of a radial length of the overlapping layer number uniformregion to a radial length of the overlapping layer number uniform regionand the overlapping layer number decreasing region may be 30% to 85%.

A ratio of a length of an electrode area corresponding to the segmentskip region to the entire length of the first electrode may be 1% to30%.

A ratio of a length of an electrode area corresponding to the heightvariable region to the entire length of the first electrode may be 1% to40%.

A ratio of a length of an electrode area corresponding to the heightuniform region to the entire length of the first electrode may be 50% to90%.

In the region divided into the plurality of segments, at least oneselected from widths of the segments in the winding direction, heightsthereof in the direction of the axis, and a lower internal angle thereofmay increase stepwise along one direction parallel to the windingdirection.

A height of a region of the second portion adjacent to the core or theouter circumference of the electrode assembly may be lower than a heightof the plurality of segments.

The plurality of segments may be bent toward the core of the electrodeassembly, and the core of the electrode assembly may not be covered bythe bent portion of a segment located closest to the core of theelectrode assembly by at least 90% or more of a diameter thereof.

In another aspect of the present disclosure, there is also provided anelectrode assembly including a positive electrode; a negative electrode;and a separator between the positive electrode and the negativeelectrode, the positive electrode, the negative electrode, and theseparator wound about an axis defining a core and an outercircumference, wherein the positive electrode has a pair of first sidesand a pair of second sides extending between the pair of first sides, afirst portion extending between the pair of first sides, and a secondportion extending between the pair of first sides, wherein the firstportion is coated with an active material along a winding direction,wherein at least a part of the second portion includes an electrode tab,wherein the second portion includes a plurality of segments that areindependently bendable from the core toward the outer circumference ofthe electrode assembly, wherein the plurality of segments are bent alonga radial direction of the electrode assembly and overlapped intomultiple layers to form a bending surface region, wherein the bendingsurface region includes an overlapping layer number uniform region inwhich the number of overlapping layers of the segments is substantiallyuniform and an overlapping layer number decreasing region locatedadjacent to the overlapping layer number uniform region and the numberof overlapping layers of the segments in the overlapping layer numberdecreasing region decreases away from the overlapping layer numberuniform region, along the radial direction, and wherein, in theoverlapping layer number uniform region, an overlapping thickness ofsegments is between 100 μm and 875 μm.

In still another aspect of the present disclosure, there is alsoprovided an electrode assembly including a positive electrode; anegative electrode; and a separator between the positive electrode andthe negative electrode, the positive electrode, the negative electrode,and the separator wound about an axis defining a core and an outercircumference, wherein the negative electrode has a pair of first sidesand a pair of second sides extending between the pair of first sides, afirst portion extending between the pair of first sides, and a secondportion extending between the pair of first sides, wherein the firstportion is coated with an active material along a winding direction,wherein at least a part of the second portion includes an electrode tab,wherein the second portion includes a plurality of segments that areindependently bendable from the core toward the outer circumference ofthe electrode assembly, wherein the plurality of segments are bent alonga radial direction of the electrode assembly and overlapped intomultiple layers to form a bending surface region, wherein the bendingsurface region includes an overlapping layer number uniform region inwhich the number of overlapping layers of the segments is substantiallyuniform and an overlapping layer number decreasing region locatedadjacent to the overlapping layer number uniform region and the numberof overlapping layers of the segments in the overlapping layer numberdecreasing region decreases away from the overlapping layer numberuniform region, along the radial direction, and wherein, in theoverlapping layer number uniform region, an overlapping thickness ofsegments is between 50 μm and 700 μm.

In another aspect of the present disclosure, there is also provided abattery including an electrode assembly including a first electrode, asecond electrode, and a separator between the first electrode and thesecond electrode, the first electrode, the second electrode, and theseparator wound about an axis defining a core and an outercircumference, wherein the first electrode has a pair of first sides anda pair of second sides extending between the pair of first sides, afirst portion extending between the pair of first sides, and a secondportion extending between the pair of first sides, wherein the firstportion is coated with an active material along a winding direction, atleast a part of the second portion includes an electrode tab, the secondportion includes a first part adjacent to the core of the electrodeassembly, a second part adjacent to the outer circumference of theelectrode assembly, and a third part between the first part and thesecond part, and the first part or the second part has a smaller heightthan the third part in the direction of the axis; a battery housingincluding a first end with a first opening and a second end oppositethereto, wherein the electrode assembly is accommodated in a spacebetween the first end and the second end, and the battery housing iselectrically connected to one of the first electrode or the secondelectrode to have a first polarity; a sealing body sealing the firstopening at the first end of the battery housing; and a terminalelectrically connected to the other of the first electrode or the secondelectrode to have a second polarity and having a surface exposed outsidethe battery housing.

The second part may have a smaller height than the third part in thedirection of the axis, the battery housing may have a beading portionpress-fitted inward at a region adjacent to the first opening at thefirst end, and an inner circumference of the beading portion facing atop edge of the electrode assembly and the second part are spaced apartby a predetermined distance.

A press-in depth D1 of the beading portion and a distance D2 from aninner circumference of the battery housing to a boundary between thesecond part and the third part may satisfy a formula D1≤D2.

The battery may further include a current collector electrically coupledto the third part; and an insulator covering the current collector andhaving an edge fixed between the inner circumference of the beadingportion and the current collector.

A diameter of the current collector may be smaller than a minimum innerdiameter of the inner circumference of the beading portion, and adiameter of the current collector may be equal to or greater than anoutermost diameter of the third part.

The current collector may be located higher than the beading portion inthe direction of the axis.

The sealing body may include a cap sealing the first opening at thefirst end of the battery housing, and a gasket between an edge of thecap and the first opening at the first end of the battery housing, andthe battery housing may include a crimping portion bent inward andsurrounding and fixing an edge of the cap together with the gasket, andthe terminal having the second polarity may be the cap.

The battery may further include a first current collector electricallyconnected to the second portion, and the terminal may be a rivetterminal installed in a hole formed in the second end of the batteryhousing to be insulated therefrom and electrically connected to thefirst current collector to have the second polarity.

The battery may further include an insulator between an inner surface ofthe bottom portion of the battery housing and an upper surface of thefirst current collector to electrically insulate the inner surface ofthe bottom portion of the battery housing and the first currentcollector.

The insulator may have a thickness corresponding to a distance betweenthe inner surface of the bottom portion of the battery housing and theupper surface of the first current collector and may be in contact withthe inner surface of the bottom portion of the battery housing and theupper surface of the first current collector.

The terminal may include a flat portion at a lower end thereof, theinsulator may have an opening for exposing the flat portion, and theflat portion may be welded to the first current collector through theopening.

The second electrode may have a pair of third sides and a pair of fourthsides extending between the pair of third sides, a third portionextending between the pair of third sides, and a fourth portionextending between the pair of third sides, wherein the third portion maybe coated with an active material along the winding direction, whereinthe second electrode may have the first polarity, and at least a part ofthe fourth portion may include an electrode tab, and wherein the batterymay further include a second current collector electrically connected tothe fourth portion and having an edge at least partially coupled to asidewall of the battery housing.

The second electrode has a pair of third sides and a pair of fourthsides extending between the pair of third sides, a third portionextending between the pair of third sides, and a fourth portionextending between the pair of third sides, wherein the third portion maybe coated with an active material along the winding direction, whereinthe second electrode may have the first polarity, and wherein at least apart of the fourth portion may include an electrode tab, wherein thebattery may further include a second current collector electricallyconnected to the fourth portion and having an edge at least partiallycoupled to a sidewall of the battery housing, and wherein the firstcurrent collector may have an outer diameter equal to or greater thanthat of the second current collector.

The first current collector and the second current collector may berespectively welded to the second portion and the fourth portion along aradial direction of the electrode assembly forming welding patterns, anda length of the welding pattern of the first current collector may belonger than a length of the welding pattern of the second currentcollector.

The welding pattern of the first current collector and the weldingpattern of the second current collector may be located substantially ata same distance from a core center of the electrode assembly.

The battery housing may include a beading portion press-fitted inward atan inner wall adjacent to the first opening at the first end, and theedge of the second current collector may be electrically connected tothe beading portion.

A region of the second current collector in electrical contact with thefourth portion may be located farther inward than an inner circumferenceof the beading portion.

The battery may include a cap having an edge supported by the beadingportion and having no polarity, a gasket between the edge of the cap andthe first opening at the first end of the battery housing, and acrimping portion bent and extended into the first opening of the batteryhousing and surrounding and fixing the edge of the cap together with thegasket, and wherein the edge of the second current collector may befixed between the beading portion and the gasket by the crimpingportion.

The edge of the second current collector may be welded to the beadingportion.

At least one of the third part or the second part may be divided into aplurality of segments that are independently bendable, and a region ofthe second portion divided into the plurality of segments may include aheight variable region in which the height of the segments variesstepwise from a first height h₁ to an N−1^(th) height h_(N-1), and aheight uniform region in which the height of the segments is maintainedas an N^(th) height h_(N) which is greater than h_(N-1), and N is aheight index and a natural number of 2 or above.

N may be a natural number of 2 to 30.

A plurality of segments may have a height h_(k), and the plurality ofsegments having the height h_(k) may be disposed in at least one windingturn, and k is a natural number of 1 to N.

The core of the electrode assembly may not be covered by a bent portionof the segment located at r_(k) by at least 90% or more of a diameterthereof, wherein r_(k) is a start radius of a winding turn including thesegment having a height h_(k), and k is a natural number of 1 to N.

The height h_(k) of the segment may satisfy the following formula:

2 mm≤h_(k)≤r_(k)−α*r_(c)

wherein r_(k) is a start radius of a winding turn including the segmenthaving a height h_(k), k is a natural number of 1 to N, r_(c) is aradius of the core, and a is 0.90 to 1.

A width of the segment in the winding direction D(r) may satisfy thefollowing formula:

1≤D(r)≤(2*π*r/360°)*45°

wherein r is a radius of a winding turn including the segment based on acore center of the electrode assembly.

In each of the plurality of segments, as the radius r of the windingturn where the segment is located based on a core center of theelectrode assembly increases, the width of segments in the windingdirection may increase or may decrease gradually or stepwise.

In each of the plurality of segments, as the radius r of the windingturn where the segment is located based on a core center of theelectrode assembly increases, heights of segments in the windingdirection may increase gradually or stepwise and then may decreasegradually or stepwise or may decrease gradually or stepwise and then mayincrease gradually or stepwise.

Each of the plurality of segments has a geometric shape in which a widthof a lower portion is greater than a width of an upper portion, and alower internal angle (θ) of a segment located in a winding turn having aradius r based on the core of the electrode assembly may fall within anangle range of the following formula:

${\cos^{- 1}( \frac{0.5*D}{r} )} \leq \theta \leq {\tan^{- 1}( \frac{2*H*\tan\theta_{refer}}{{2*H} - {p*\tan\theta_{refer}}} )}$

wherein D is a width of the segment in the winding direction, r is aradius of the winding turn including the segment, H is a height of thesegment, and p is a separation pitch of the segment.

The lower internal angle of the plurality of segments may increaseindividually or in groups in the range of 60 to 85 degrees in onedirection parallel to the winding direction.

In the height variable region and the height uniform region, a maximumheight h_(max) of the segments may satisfy the following formula:

h_(max)≤W_(foil)−W_(scrap,min)−W_(margin,min)−W_(gap)

wherein W_(foil) is a width of a current collector foil before segmentsare formed, W_(scrap,min) is a width corresponding to a minimum cutscrap margin when segments are formed by cutting the current collectorfoil, W_(margin,min) is a width corresponding to a minimum meanderingmargin of the separator, and W_(gap) is a width corresponding to aninsulation gap between an end of the separator and an end of the secondelectrode facing the first electrode with the separator therebetween.

The first electrode may be a positive electrode and the insulation gapmay be in the range of 0.2 mm to 6 mm.

The first electrode may be a negative electrode and the insulation gapmay be in the range of 0.1 mm to 2 mm.

The minimum cut scrap margin may be in the range of 1.5 mm to 8 mm.

The minimum meandering margin may be in the range of 0 to 1 mm.

The minimum cut scrap margin may be zero.

The heights of the segments disposed in the height variable region mayincrease gradually or stepwise within the range of 2 mm to 10 mm.

At least one of the third part or the second part may be divided into aplurality of segments that are independently bendable, the electrodeassembly may include a segment skip region having no segment, a heightvariable region where segments have variable heights, and a heightuniform region where segments have a substantially uniform height inorder along a radial direction, based on a cross section along thedirection of the axis, and the plurality of segments may be disposed inthe height variable region and the height uniform region and bent alongthe radial direction of the electrode assembly forming a bending surfaceregion.

The first part may not be divided into segments, and the segment skipregion may correspond to the first part.

A ratio of a radial length of the segment skip region to a radius of theelectrode assembly except for the core in the radial direction of theelectrode assembly may be 10% to 40%.

A ratio of a radial length of the height variable region to a radiallength corresponding to the height variable region and the heightuniform region in the radial direction of the electrode assembly may be1% to 50%.

A ratio of a length of an electrode area corresponding to the segmentskip region to the entire length of the first electrode may be 1% to30%.

A ratio of a length of an electrode area corresponding to the heightvariable region to the entire length of the first electrode may be 1% to40%.

A ratio of a length of an electrode area corresponding to the heightuniform region to the entire length of the first electrode may be 50% to90%.

The plurality of segments may form a plurality of segment groups alongone direction parallel to the winding direction of the electrodeassembly, and segments belonging to the same segment group may besubstantially the same as each other in terms of a width in the windingdirection and a height in the direction of the axis.

Widths of the segments belonging to the same segment group in thewinding direction or heights thereof in the direction of the axis, orboth may increase stepwise along one direction parallel to the windingdirection of the electrode assembly.

The plurality of segment groups may include a combination of segmentgroups in which W3/W2 is smaller than W2/W1, and wherein W1, W2 and W3are widths in the winding direction of three segment groups successivelyadjacent to each other in one direction parallel to the windingdirection of the electrode assembly.

When the number of segments meeting a virtual line parallel to thedirection of the axis at any radial location of the bending surfaceregion based on a core center of the electrode assembly is defined asthe number of overlapping layers of segments at the corresponding radiallocation, the bending surface region may include an overlapping layernumber uniform region in which the number of overlapping layers ofsegments is substantially uniform from the core toward the outercircumference and an overlapping layer number decreasing region locatedadjacent to the overlapping layer number uniform region and the numberof overlapping layers of segments in the overlapping layer numberdecreasing region may decrease away from the overlapping layer numberuniform region.

In the overlapping layer number uniform region, the number ofoverlapping layers of the segments may be 10 or more.

In the overlapping layer number uniform region, the number ofoverlapping layers of the segments may be 10 to 35.

A start radius of the overlapping layer number uniform region maycorrespond to a start radius of the height variable region based on thecore center of the electrode assembly.

A ratio of a radial length of the overlapping layer number uniformregion to a radial length of the overlapping layer number uniform regionand the overlapping layer number decreasing region may be 30% to 85%.

The first electrode may be a positive electrode, and in the overlappinglayer number uniform region, an overlapping thickness of segments may bebetween 100 μm and 875 μm.

The battery may further include a current collector welded to theoverlapping layer number uniform region such that at least a part of awelding region of the current collector overlaps with the overlappinglayer number uniform region, and wherein the first electrode may be apositive electrode and the overlapping layers of segments in the weldingregion may have a thickness in the range of 100 μm to 875 μm.

The first electrode may be a negative electrode, and in the overlappinglayer number uniform region, an overlapping thickness of segments may bebetween 50 μm and 700 μm.

The battery may further include a current collector welded to theoverlapping layer number uniform region such that at least a part of awelding region of the current collector overlaps with the overlappinglayer number uniform region, and wherein the first electrode may be anegative electrode and the overlapping layers of segments in the weldingregion may have a thickness in the range of 50 μm to 700 μm.

At least one of the third part or the second part may be divided into aplurality of segments that are independently bendable, wherein theplurality of segments may have a cut groove between segments adjacent toeach other along the winding direction, and a lower portion of the cutgroove may include a bottom portion, and a round portion connecting bothends of the bottom portion to sides of the segments which are at bothsides of the cut groove.

The round portion may have a radius of curvature greater than 0 andequal to or smaller than 0.1 mm.

The round portion may have a radius of curvature of 0.01 mm to 0.05 mm.

The bottom portion may be flat.

A separation pitch defined as an interval between two points at whichlines extending from the sides of two segments located at both sides ofthe cut groove meet a line extending from the bottom portion of the cutgroove may be 0.05 mm to 1.00 mm.

The plurality of segments may be made of an aluminum foil, and aseparation pitch defined as an interval between two points at whichlines extending from the sides of two segments located at both sides ofthe cut groove meet a line extending from a lower end of the cut groovemay be 0.05 mm to 1.00 mm.

The bottom portion of the cut groove may be spaced apart from the firstportion by a predetermined distance.

The predetermined distance may be 0.2 mm to 4 mm.

A bending region of the plurality of segments in a radial direction ofthe electrode assembly may be located in the range of 0 to 1 mm above alower end of the cut groove.

An insulating coating layer may be formed at a boundary between thefirst portion and a region of the second portion provided in a sectionwhere the bottom portion of the cut groove and the first portion areseparated.

The insulating coating layer may include a polymer resin and aninorganic filler dispersed in the polymer resin.

The insulating coating layer may be formed to cover a boundary portionof the first portion and the second portion along the winding direction.

The insulating coating layer may be formed to cover the boundary portionof the first portion and the second portion along the direction of theaxis by a width of 0.3 mm to 5 mm. An end of the insulating coatinglayer may be located within the range of −2 mm to 2 mm along thedirection of the axis with respect to an end of the separator.

The insulating coating layer may be exposed beyond the separator.

A lower end of the cut groove and the insulating coating layer may bespaced apart by a distance of 0.5 mm to 2 mm.

An end of the insulating coating layer in the direction of the axis maybe located within the range of −2 mm to +2 mm based on the lower end ofthe cut groove.

The battery further include a current collector welded to the bendingsurface region, wherein, in the radial direction of the electrodeassembly, a welding region of the current collector may overlap with theoverlapping layer number uniform region by at least 50%. In the radialdirection of the electrode assembly, a region of the welding region ofthe current collector not overlapping with the overlapping layer numberuniform region may overlap with the overlapping layer number decreasingregion.

An edge of the current collector may be disposed on the bending surfaceregion to cover an end of a bent portion of the outermost segment in theradial direction of the electrode assembly and welded to the bendingsurface region.

A welding strength of the current collector to the welding region may be2 kgf/cm² or more.

A welding strength of the current collector to the welding region may be4 kgf/cm² or more.

The second portion may be made of a metal foil, and the metal foil mayhave an elongation of 1.5% to 3.0% and a tensile strength of 25 kgf/mm²to 35 kgf/mm².

The metal foil may be an aluminum foil.

The first electrode may have a camber length smaller than 20 mm.

In the first portion, a ratio of a length of a short side parallel tothe direction of the axis to a length of a long side parallel to thewinding direction may be 1% to 4%.

In still another aspect of the present disclosure, there is alsoprovided a battery including an electrode assembly including a firstelectrode, a second electrode, and a separator between the firstelectrode and the second electrode, the first electrode, the secondelectrode, and the separator are wound about an axis defining a core andan outer circumference, wherein the first electrode has a pair of firstsides and a pair of second sides extending between the pair of firstsides, a first portion extending between the pair of first sides, and asecond portion extending between the pair of first sides, wherein thefirst portion is coated with an active material along a windingdirection, the second portion includes a region divided into a pluralityof segments that are independently bendable from the core toward theouter circumference of the electrode assembly, the plurality of segmentsare bent along a radial direction of the electrode assembly forming abending surface region, and the bending surface region includes anoverlapping layer number uniform region in which the number ofoverlapping layers of the segments is 10 or more and an overlappinglayer number decreasing region located adjacent to the overlapping layernumber uniform region and the number of overlapping layers of thesegments in the overlapping layer number decreasing region decreasesaway from the overlapping layer number uniform region, along the radialdirection; a battery housing including a first end with first openingand a second end opposite thereto, wherein the electrode assembly isaccommodated in a space between the first end and the second end, andthe battery housing is electrically connected to one of the firstelectrode or the second electrode to have a first polarity; a sealingbody sealing the first opening at the first end of the battery housing;and a terminal electrically connected to the other of the firstelectrode or the second electrode to have a second polarity and having asurface exposed outside the battery housing.

In yet another aspect of the present disclosure, there is also provideda battery including an electrode assembly including a positiveelectrode, a negative electrode, and a separator between the positiveelectrode and the negative electrode, the positive electrode, thenegative electrode, and the separator wound about an axis defining acore and an outer circumference, wherein the positive electrode has apair of first sides and a pair of second sides extending between thepair of first sides, a first portion extending between the pair of firstsides, and a second portion extending between the pair of first sides,wherein the first portion is coated with an active material along awinding direction, at least a part of the second portion includes anelectrode tab, the second portion includes a plurality of segments thatare independently bendable from the core toward the outer circumferenceof the electrode assembly, the plurality of segments are bent along aradial direction of the electrode assembly and overlapped into multiplelayers to form a bending surface region, the bending surface regionincludes an overlapping layer number uniform region in which the numberof overlapping layers of the segments is substantially uniform and anoverlapping layer number decreasing region located adjacent to theoverlapping layer number uniform region and the number of overlappinglayers of the segments in the overlapping layer number decreasing regiondecreases away from the overlapping layer number uniform region, alongthe radial direction, and an overlapping thickness of segments isbetween 100 μm to 875 μm in the overlapping layer number uniform region;a battery housing including a first end with a first opening and asecond end opposite thereto, wherein the electrode assembly isaccommodated in a space between the first end and the second end, andthe battery housing is electrically connected to one of the positiveelectrode or the negative electrode to have a first polarity; a sealingbody sealing the first opening at the first end of the battery housing;and a terminal electrically connected to the other of the positiveelectrode or the negative electrode to have a second polarity and havinga surface exposed outside the battery housing.

The battery may further include a current collector welded to theoverlapping layer number uniform region such that at least a part of awelding region of the current collector overlaps with the overlappinglayer number uniform region, and wherein the overlapping layers ofsegments in the welding region may have a thickness in the range of 100μm to 875 μm.

In another aspect of the present disclosure, there is also provided abattery including an electrode assembly including a positive electrode,a negative electrode, and a separator between the positive electrode andthe negative electrode, the positive electrode, the negative electrode,and the separator wound about an axis defining a core and an outercircumference, wherein the negative electrode has a pair of first sidesand a pair of second sides extending between the pair of first sides, afirst portion extending between the pair of first sides, and a secondportion extending between the pair of first sides, the first portion iscoated with an active material along a winding direction, at least apart of the second portion includes an electrode tab, the second portionincludes a plurality of segments that are independently bendable fromthe core toward the outer circumference of the electrode assembly, theplurality of segments are bent along a radial direction of the electrodeassembly and overlapped into multiple layers to form a bending surfaceregion, the bending surface region includes an overlapping layer numberuniform region in which the number of overlapping layers of the segmentsis substantially uniform and an overlapping layer number decreasingregion located adjacent to the overlapping layer number uniform regionand the number of overlapping layers of the segments in the overlappinglayer number decreasing region decreases away from the overlapping layernumber uniform region, along the radial direction, and an overlappingthickness of segments is between 50 μm to 700 μm in the overlappinglayer number uniform region; a battery housing including a first endwith a first opening and a second end opposite thereto, wherein theelectrode assembly is accommodated in a space between the first end andthe second end, and the battery housing is electrically connected to oneof the first electrode or the second electrode to have a first polarity;a sealing body sealing the first opening at the first end of the batteryhousing; and a terminal electrically connected to the other of the firstelectrode or the second electrode to have a second polarity and having asurface exposed to the outside.

The battery may further include a current collector welded to theoverlapping layer number uniform region such that at least a part of awelding region of the current collector overlaps with the overlappinglayer number uniform region, and wherein the overlapping layers ofsegments in the welding region may have a thickness in the range of 50μm to 700 μm.

In another aspect of the present disclosure, there is also provided abattery pack that includes a plurality of batteries described above.

A ratio of diameter to height of each battery may be greater than 0.4.

Each battery may have a form factor of 46110, 4875, 48110, 4880 or 4680.

Each battery may have a resistance of 4 milliohms or less.

The plurality of batteries may be arranged in a predetermined number ofcolumns, such that the terminal of each battery and an outer surface ofthe second end of the battery housing of each battery may facevertically upward.

The battery pack may further include a plurality of bus bars connectingthe plurality of batteries in series and in parallel, wherein theplurality of bus bars may be disposed at an upper portion of adjacentbatteries among the plurality of batteries, and wherein each of the busbars may include: a body portion extending between the adjacentbatteries; a plurality of first bus bar terminals extending in a firstside direction of the body portion and electrically coupled to theterminals of the adjacent batteries located in the first side direction;and a plurality of second bus bar terminals extending in a second sidedirection of the body portion opposite the first side direction andelectrically coupled to an outer surface of the second end of thebattery housing of each of the adjacent batteries located in the secondside direction of the body portion.

In yet another aspect of the present disclosure, there is also provideda vehicle that includes the battery pack described above.

Finally, in another aspect of the present disclosure, there is alsoprovided a method of producing a battery including forming an electrodeassembly having a first electrode, a second electrode and a separatorbetween the first electrode and the second electrode, wherein the firstelectrode, the second electrode, and the separator are wound about anaxis defining a core and a circumferential surface of the electrodeassembly, wherein the first electrode has a pair of first sides and apair of second sides extending between the pair of first sides, a firstportion extending between the pair of first sides, and a second portionextending between the pair of first sides, wherein the first portion iscoated with an active material along a winding direction, wherein atleast a part of the second portion includes an electrode tab, whereinthe second portion includes a first part adjacent to the core of theelectrode assembly, a second part adjacent to the outer circumference ofthe electrode assembly, and a third part between the first part and thesecond part, and the first part or the second part has a smaller heightthan the third part in the direction of the axis; forming a batteryhousing having a first end with a first opening and a second endopposite the first end, the battery housing accommodating the electrodeassembly in a space between the first end and the second end andelectrically connected to one of the first electrode or the secondelectrode to have a first polarity; forming a sealing body sealing thefirst opening at the first end of the battery housing; and forming aterminal electrically connected to the other of the first electrode orthe second electrode to have a second polarity and having a surfaceexposed outside the battery housing.

Advantageous Effects

According to an embodiment of the present disclosure, since the uncoatedportions themselves protruding from the upper and lower portions of theelectrode assembly are used as electrode tabs, it is possible to reducethe internal resistance of the battery and increase the energy density.

According to another embodiment of the present disclosure, since thestructure of the uncoated portion of the electrode assembly is improvedso that the electrode assembly does not interfere with the innercircumference of the battery in the process of forming the beadingportion of the battery housing, it is possible to prevent a shortcircuit in the cylindrical battery caused by partial deformation of theelectrode assembly.

According to still another embodiment of the present disclosure, sincethe structure of the uncoated portion of the electrode assembly isimproved, it is possible to prevent the uncoated portion from being tornwhen the uncoated portion is bent, and the number of overlapping layersof the uncoated portions is sufficiently increased to improve weldingstrength of the current collector.

According to still another embodiment of the present disclosure, it ispossible to improve physical properties of a region where the currentcollector is welded, by applying a segment structure to the uncoatedportion of the electrode and optimizing the dimensions (width, height,separation pitch) of the segments to sufficiently increase the number ofoverlapping layers of the segments in an area used as a welding targetregion.

According to still another embodiment of the present disclosure, it ispossible to provide an electrode assembly with improved energy densityand reduced resistance by applying a structure in which a currentcollector is welded over a large area to a bending surface region formedby bending the segments.

According to still another embodiment of the present disclosure, it ispossible to provide a cylindrical battery having an improved design soas to perform electrical wiring at an upper portion thereof.

According to still another embodiment of the present disclosure, sincethe structure of the uncoated portion adjacent to the core of theelectrode assembly is improved, it is possible to prevent the cavity inthe core of the electrode assembly from being blocked when the uncoatedportion is bent. Thus, the electrolyte injection process and the processof welding the battery housing (or the terminal) and the currentcollector may be carried out easily.

According to still another embodiment of the present disclosure, it ispossible to provide a cylindrical battery having a structure that has alow internal resistance, prevents internal short circuit and improveswelding strength of the current collector and the uncoated portion, anda battery pack and a vehicle including the cylindrical battery.

In particular, the present disclosure may provide a cylindrical batteryhaving a diameter to height ratio of 0.4 or more and a resistance of 4milliohms (mohm) or less, and a battery pack and a vehicle including thesame.

In addition, the present disclosure may have several other effects, andsuch effects will be described in each embodiment, or any descriptionthat can be easily inferred by a person skilled in the art will beomitted for an effect.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate embodiments of the presentdisclosure and together with the foregoing disclosure, serve to providefurther understanding of the technical features of the presentdisclosure, and thus, the present disclosure is not construed as beinglimited to the drawing.

FIG. 1 is a plan view showing a structure of an electrode used formanufacturing a conventional tab-less cylindrical battery.

FIG. 2 is a diagram showing an electrode winding process of theconventional tab-less cylindrical battery.

FIG. 3 is a diagram showing a process of welding a current collector toa bent surface region of an uncoated portion in the conventionaltab-less cylindrical battery.

FIG. 4 is a plan view showing a structure of an electrode according tothe first embodiment of the present disclosure.

FIG. 5 is a plan view showing a structure of an electrode according tothe second embodiment of the present disclosure.

FIG. 6 is a plan view showing a structure of an electrode according tothe third embodiment of the present disclosure.

FIG. 7 a is a plan view showing a structure of an electrode according tothe fourth embodiment of the present disclosure.

FIG. 7 b is a diagram showing the definitions of width, height andseparation pitch of a segment according to an embodiment of the presentdisclosure.

FIG. 7 c is a diagram showing an arc formed by a lower end of a segmentdefining a width of the segment based on a core center of an electrodeassembly, when the electrode is wound according to an embodiment of thepresent disclosure.

FIG. 7 d is a diagram showing a relationship of heights h₁, h₂, h₃, h₄of the segments, a core radius (r_(c)), and radii r₁, r₂, r₃, r₄ of awinding turns where the segments start appearing, according to anembodiment the present disclosure.

FIG. 7 e is a diagram for determining a maximum value (h_(max)) of theheight (H) of the segments in a height variable region of the segments.

FIG. 7 f is a schematic diagram for illustrating a formula fordetermining a lower internal angle (θ) of the segment.

FIG. 7 g is a plan view showing a modified structure of the electrodeaccording to the fourth embodiment of the present disclosure.

FIG. 7 h is a top plan view showing an independent region where aplurality of segments may be located, when the electrode according tothe modification of the present disclosure is wound as an electrodeassembly.

FIG. 8 a is a plan view showing a structure of an electrode according tothe fifth embodiment of the present disclosure.

FIG. 8 b is a diagram showing the definitions of width, height andseparation pitch of a segment according to another embodiment of thepresent disclosure.

FIG. 8 c is a plan view showing a modified structure of the electrodeaccording to the fifth embodiment of the present disclosure.

FIG. 9 is a diagram showing segment structures according to variousmodifications of the present disclosure.

FIG. 10 a is a diagram showing a cross section of a bending surfaceregion formed by bending the segment toward the core of the electrodeassembly.

FIG. 10 b is a top perspective view schematically showing an electrodeassembly in which the bending surface region is formed.

FIG. 10 c is a graph showing results obtained by counting the number ofoverlapping layers of segments along a radial direction in a bendingsurface region of a positive electrode formed at an upper portion of theelectrode assemblies according to Examples 1-1 to 1-7 and a comparativeexample.

FIG. 10 d is a graph showing results obtained by counting the number ofoverlapping layers of segments measured along the radial direction in abending surface region of a positive electrode formed at an upperportion of the electrode assemblies according to Examples 2-1 to 2-5,Examples 3-1 to 3-4, Examples 4-1 to 4-3, and Examples 5-1 and 5-2.

FIG. 10 e is a graph showing results obtained by counting the number ofoverlapping layers of segments measured along the radial direction in abending surface region of a positive electrode formed at an upperportion of the electrode assemblies according to Examples 6-1 to 6-6 andExamples 7-1 to 7-6.

FIG. 10 f is a top plan view of the electrode assembly showing anoverlapping layer number uniform region b1 and an overlapping layernumber decreasing region b2 in the bending surface region of the segmentaccording to an embodiment of the present disclosure.

FIG. 11 is a sectional view showing a jelly-roll type electrode assemblyin which the electrode of the first embodiment is applied to a firstelectrode (a positive electrode) and a second electrode (a negativeelectrode), taken along the Y-axis direction (winding axis direction).

FIG. 12 is a sectional view showing a jelly-roll type electrode assemblyin which the electrode of the second embodiment is applied to the firstelectrode (the positive electrode) and the second electrode (thenegative electrode), taken along the Y-axis direction (winding axisdirection).

FIG. 13 is a sectional view showing a jelly-roll type electrode assemblyin which any one of the electrodes of the third to fifth embodiments(modifications thereof) is applied to the first electrode (the positiveelectrode) and the second electrode (the negative electrode), takenalong the Y-axis direction (winding axis direction).

FIG. 14 is a sectional view showing an electrode assembly according tostill another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

FIG. 15 is a sectional view showing an electrode assembly according tostill another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

FIG. 16 is a sectional view showing an electrode assembly according tostill another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

FIG. 17 is a sectional view showing a cylindrical battery according toan embodiment of the present disclosure, taken along the Y-axisdirection.

FIG. 18 is a sectional view showing a cylindrical battery according toanother embodiment of the present disclosure, taken along the Y-axisdirection.

FIG. 19 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis direction.

FIG. 20 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 21 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 22 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 23 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 24 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 25 is a sectional view showing a cylindrical battery according tostill another embodiment of the present disclosure, taken along theY-axis.

FIG. 26 is a top plan view showing a structure of a first currentcollector according to an embodiment of the present disclosure.

FIG. 27 is a perspective view showing a structure of a second currentcollector according to an embodiment of the present disclosure.

FIG. 28 is a top plan view showing a state in which a plurality ofcylindrical batteries are electrically connected.

FIG. 29 is a partially enlarged view of FIG. 28 .

FIG. 30 is a diagram schematically showing a battery pack according toan embodiment of the present disclosure.

FIG. 31 is a diagram schematically showing a vehicle including thebattery pack according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. Prior to thedescription, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentdisclosure on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation.

Therefore, the descriptions provided herein are just examples for thepurpose of illustrations only, not intended to limit the scope of thedisclosure, so it should be understood that other equivalents andmodifications could be made thereto without departing from the scope ofthe disclosure.

In addition, in order to help understanding of the invention, in theaccompanying drawings, some components may not be drawn to scale, buttheir dimensions may be exaggerated. Also, the same reference numbersmay be assigned to the same components in different embodiments.

When it is explained that two objects are ‘identical’, this means thatthese objects are ‘substantially identical’. Accordingly, thesubstantially identical objects may include deviations considered low inthe art, for example, deviations within 5%. Also, when it is explainedthat certain parameters are uniform in a region, this may mean that theparameters are uniform in terms of an average in the correspondingregion.

First, an electrode assembly according to an embodiment of the presentdisclosure will be described. The electrode assembly may be a jelly-rolltype electrode assembly in which a first electrode and a secondelectrode having a sheet shape and a separator interposed therebetweenare wound in one direction. The first electrode may have a pair of firstsides along a winding axis of the electrode assembly and a pair ofsecond sides extending between the pair of first sides in a windingdirection of the electrode assembly. The second electrode may have apair of third sides along a winding axis of the electrode assembly and apair of fourth sides extending between the pair of third sides in awinding direction of the electrode assembly. The first and third sidesof the first electrode and the second electrode, respectively, may beshort sides, and the second and fourth sides of the first electrode andthe second electrode, respectively, may be long sides. However, thepresent invention is not limited to a specific kind of the electrodeassembly.

Preferably, at least one of the first electrode and the second electrodeincludes an uncoated portion not coated with an active material at along side end in the winding direction. At least a part of the uncoatedportion is used as an electrode tab by itself. The uncoated portionincludes a core-side uncoated portion adjacent to a core of theelectrode assembly, a circumferential uncoated portion adjacent to anouter circumference of the electrode assembly, and an intermediateuncoated portion interposed between the core-side uncoated portion andthe circumferential uncoated portion. For example, in the case of thefirst electrode, a region extending between the pair of first sides maybe coated with an active material and may be referred to as a firstportion, and another region extending between the pair of first sidesmay not be coated with the active material and may be referred to as asecond portion. Similarly, in the case of the second electrode, a regionextending between the pair of third sides may be coated with an activematerial and may be referred to as a third portion, and another regionextending between the pair of fourth sides may not be coated with theactive material and may be referred to as a fourth portion.

Preferably, at least one of the core-side uncoated portion and thecircumferential uncoated portion has a relatively lower height than theintermediate uncoated portion.

FIG. 4 is a plan view showing a structure of an electrode 40 accordingto the first embodiment of the present disclosure.

Referring to FIG. 4 , the electrode 40 of the first embodiment includesa current collector made of metal foil and an active material layer 42.The metal foil may be metal with conductivity, for example aluminum orcopper, and is appropriately selected according to the polarity of theelectrode 40. The active material layer 42 is formed on at least onesurface of the current collector 41. The active material layer 42 isformed along the winding direction X. The electrode 40 includes anuncoated portion 43 at the long side end in the winding direction X. Theuncoated portion 43 is a partial area of the current collector 41 wherethe active material is not coated. The region of the current collector41 where the active material is formed may be called an active materialportion.

In the electrode 40, the width of the active material portion in adirection along a short side of the current collector 41 may be 50 mm to120 mm, and the length of the active material portion in a directionalong a long side of the current collector 41 may be 3 m to 5 m.Accordingly, the ratio of the short side to the long side of the activematerial portion may be 1% to 4%.

Preferably, in the electrode 40, the width of the active materialportion in a direction along a short side of the current collector 41may be 60 mm to 70 mm, and the length of the active material portion ina direction along a long side of the current collector 41 may be 3 m to5 m. Accordingly, the ratio of the short side to the long side of theactive material portion may be 1.2% to 2.3%.

The ratio of the short side to the long side of the active materialportion is significantly smaller than the ratio of the short side to thelong side of an active material portion in the electrode used in acylindrical battery having a form factor of 1865 or 2170, which is 6% to11%.

Preferably, the current collector 41 may have an elongation of 1.5% to3.0% and a tensile strength of 25 kgf/mm² to 35 kgf/mm². The elongationand tensile strength may be measured according to the measurement methodof IPC-TM-650. The electrode 40 is manufactured by forming an activematerial layer 42 on the current collector 41 and then compressing thesame. During the compression, a region of the uncoated portion 43 and aregion of the active material layer 42 have different elongations.Therefore, a swell occurs on the electrode 40 after the compression, andthe swell is more severe as the electrode 40 is longer.

Optimization of the elongation and tensile strength for the currentcollector 41 reduces the camber length after the compression to lessthan 20 mm when the length of the electrode 40 is about 4 m. The camberlength is a maximum amount of deflection of the electrode 20 in thewinding direction X when the swelled electrode 20 is unfolded. Themaximum amount of deflection may be measured at a circumferential end.The electrode 40 in which the elongation and tensile strength of thecurrent collector 41 are optimized has a small camber length, so thatthere is no meandering defect while notching the uncoated portion 43 orwinding the electrode 40.

The current collector 41 tends to be easily ruptured as the elongationis small. When the elongation of the current collector 41 is less than1.5%, the rolling process efficiency of the current collector 41 isdeteriorated, and thus, when the electrode 40 coated with the activematerial layer 42 is compressed onto the current collector 41, adisconnection may occur in the current collector 41. Meanwhile, when theelongation of the current collector 41 exceeds 3.0%, the active materialportion of the electrode 40 is elongated more, and accordingly thecamber length increases significantly. When the tensile strength of thecurrent collector 41 is less than kgf/mm² or more than 35 kgf/mm², theelectrode process efficiency of the electrode 40 is deteriorated.

The camber phenomenon is particularly problematic in a positiveelectrode current collector made of an aluminum foil. According to thepresent disclosure, if an aluminum foil having an elongation of 1.5% to3.0% and a tensile strength of 25 kgf/mm² to 35 kgf/mm² is used as acurrent collector, the camber phenomenon may be suppressed. It ispreferable that an active material layer is formed on the currentcollector to serve as a positive electrode.

Preferably, an insulating coating layer 44 may be formed at a boundarybetween the active material layer 42 and the uncoated portion 43. Theinsulating coating layer 44 is formed such that at least a part thereofoverlaps with the boundary between the active material layer 42 and theuncoated portion 43. The insulating coating layer 44 prevents a shortcircuit between two electrodes having different polarities and facingeach other with a separator interposed therebetween. The insulatingcoating layer 44 has a width of 0.3 mm to 5 mm and thus may cover theboundary portion of the active material layer 42 and the uncoatedportion 43. The width of the insulating coating layer 44 may vary in awinding direction of the electrode 40. The insulating coating layer 44contains a polymer resin and may contain inorganic fillers such asAl₂O₃. The portion of the current collector 41 covered by the insulatingcoating layer 44 is not an area coated with an active material layer andthus may be regarded as an uncoated portion.

The uncoated portion 43 may comprise a core-side uncoated portion B1adjacent to the core side of the electrode assembly, a circumferentialuncoated portion B3 adjacent to the outer circumference side of theelectrode assembly, and an intermediate uncoated portion B2 interposedbetween the core-side uncoated portion B1 and the circumferentialuncoated portion B3.

The core-side uncoated portion B1, the circumferential uncoated portionB3 and the intermediate uncoated portion B2 may be defined as anuncoated portion of a region adjacent to the core, an uncoated portionof a region adjacent to the outer circumference, and an uncoated portionof a remaining region excluding the above, respectively, when theelectrode 40 is wound into a jelly-roll type electrode assembly.

Hereinafter, the core-side uncoated portion B1, the circumferentialuncoated portion B3, and the intermediate uncoated portion B2 will bereferred to as a first part, a second part, and a third part,respectively.

In one example, the first part B1 may be an uncoated portion of theelectrode area including an innermost winding turn, and the second partB3 may be an uncoated portion of the electrode area including anoutermost winding turn.

In another example, the boundary of B1/B2 may be suitably defined as apoint at which the height (or, change pattern) of the uncoated portionsubstantially changes from the core of the electrode assembly to theouter circumference, or a certain percentage (%) point based on theradius of the electrode assembly (e.g., 5% point, 10% point, 15% pointof the radius, etc.).

The boundary of B2/B3 is a point at which the height (or, changepattern) of the uncoated portion substantially changes from the outercircumference of the electrode assembly to the core, or a certainpercentage (%) point based on the radius of the electrode assembly(e.g., 85% point, 90% point, 95% point of the radius, etc.). When theboundary of B1/B2 and the boundary of B2/B3 are specified, the thirdpart B2 may be specified automatically.

If only the boundary of B1/B2 is specified, the boundary of B2/B3 may beappropriately selected at a point near the circumference of theelectrode assembly. In an example, the second portion may be defined asan uncoated portion of the electrode region that constitutes anoutermost winding turn. Conversely, if only the boundary of B2/B3 isspecified, the boundary of B1/B2 may be appropriately selected at apoint near the core of the electrode assembly. In an example, the firstpart B1 may be defined as an uncoated portion of the electrode regionthat constitutes an innermost winding turn.

In the first embodiment, the height of the uncoated portion 43 is notconstant and there is a relative difference in the winding direction X.That is, the height (length in the Y-axis direction) of the second partB3 is relatively smaller than that of the first part B1 and the thirdpart B2.

FIG. 5 is a plan view showing a structure of an electrode 45 accordingto the second embodiment of the present disclosure.

Referring to FIG. 5 , the electrode 45 of the second embodiment differsfrom that of the first embodiment only in that the height of the secondpart B3 gradually decreases toward the outer circumference, and theother configuration is substantially the same.

In one modification, the second part B3 may be transformed into a stepshape (see dotted lines) in which the height is decreased stepwise.

FIG. 6 is a plan view showing a structure of an electrode 50 accordingto the third embodiment of the present disclosure.

Referring to FIG. 6 , in the electrode 50 of the third embodiment, theheights of the first part B1 and the second part B3 are 0 or more andrelatively smaller than that of the third part B2. In addition, theheights of the first part B1 and the second part B3 may be the same ordifferent from each other.

Preferably, the height of the third part B2 may have a step shape thatincreases stepwise from the core to the outer circumference.

Patterns 1 to 7 classify the third part B2 based on the position wherethe height of the uncoated portion 43 changes. Preferably, the number ofpatterns and the height (length in the Y-axis direction) and width(length in the X-axis direction) of each pattern may be adjusted todisperse stress as much as possible during the bending process of theuncoated portion 43. The stress dispersion is to prevent the uncoatedportion 43 from being torn when the uncoated portion is bent toward thecore of the electrode assembly.

The width (d_(B1)) of the first part B1 is designed by applying acondition that the core of the electrode assembly is not covered whenthe patterns of the third part B2 are bent toward the core. The coremeans a cavity existing at the winding center of the electrode assembly.

In one example, the width (d_(B1)) of the first part B1 may increase inproportion to the bending length of Pattern 1. The bending lengthcorresponds to the height of the pattern based on the bending point ofthe pattern.

Preferably, the width (d_(B1)) of the first part B1 may be set so thatthe radial width of the winding turns formed by the first part B1 isequal to or greater than the bending length of Pattern 1. In a modifiedexample, the width (d_(B1)) of the first part B1 may be set so that thevalue obtained by subtracting the radial width of the winding turnsformed by the first part B1 from the bending length of Pattern 1 is lessthan 0 or equal to or less than 10% of the radius of the core.

In a specific example, when the electrode 60 is used to manufacture anelectrode assembly of a cylindrical battery having a form factor of4680, the width (d_(B1)) of the first part B1 is set to 180 to 350 mmaccording to the diameter of the core of the electrode assembly and thebending length of Pattern 1.

In an embodiment, the width of each pattern may be designed toconstitute one or more winding turns of the electrode assembly.

In one modification, the height of the third part B2 may have a stepshape that increases and then decreases from the core to the outercircumference.

In another modification, the second part B3 may be modified to have thesame structure as the second embodiment.

In still another modification, the pattern structure applied to thethird part B2 may be expanded to the second part B3 (see a dotted line).

FIG. 7 a is a plan view showing a structure of an electrode 60 accordingto the fourth embodiment of the present disclosure.

Referring to FIG. 7 a in the electrode 60 of the fourth embodiment, theheights of the first part B1 and the second part B3 in the winding axis(Y) direction are 0 or more and relatively smaller than that of thethird part B2. In addition, the height of the first part B1 and thesecond part B3 in the winding axis (Y) direction may be the same ordifferent.

Preferably, at least a partial region of the third part B2 may include aplurality of segments 61. The plurality of segments 61 may increase inheight stepwise from the core to the outer circumference. The pluralityof segments 61 have a geometric shape in which the width graduallydecreases from the bottom to the top. Preferably, the geometric shape isa trapezoidal shape. As will be explained later, the shape of thegeometric figure may be modified in various ways.

The segment 61 may be formed by laser notching. The segment 61 may beformed by a known metal foil cutting process such as ultrasonic cuttingor punching.

In the fourth embodiment, in order to prevent the active material layer42 and/or the insulating coating layer 44 from being damaged duringbending of the uncoated portion 43, it is preferable to provide apredetermined gap between a bottom G (see FIG. 7 b ) of a cut groove 63between the segments 61 and the active material layer 42. This isbecause stress is concentrated near the bottom of the cut groove 63 whenthe uncoated portion 43 is bent. The gap is 0.2 mm to 4 mm, moreparticularly, 1.5 mm to 2.5 mm. The gap may by vary along a windingdirection of the electrode 60. If the gap is adjusted within thecorresponding numerical range, it is possible to prevent the activematerial layer 42 and/or the insulating coating layer 44 from beingdamaged near the bottom of the cut groove 63 by the stress generatedduring bending of the uncoated portion 43. In addition, the gap mayprevent the active material layer 42 and/or the insulating coating layer44 from being damaged due to tolerances during notching or cutting ofthe segments 61. The lower end of the cut groove 63 and the insulatingcoating layer 44 may be separated by 0.5 mm to 2.0 mm. When theelectrode 60 is wound, the end of the insulating coating layer 44 in thewinding axis (Y) direction may be located in the range of −2 mm to 2 mmalong the winding axis direction with respect to the end of theseparator. The insulating coating layer 44 may prevent a short circuitbetween two electrodes having different polarities facing each otherwith a separator interposed therebetween and support the bending pointwhen the segments 61 are bent. In order to improve the effect ofpreventing a short circuit between the two electrodes, the insulatingcoating layer 44 may be exposed out of the separator. In addition, inorder to further maximize the effect of preventing a short circuitbetween the two electrodes, the width of the insulating coating layer 44may be increased so that its end in the winding axis (Y) direction islocated higher than the lower end of the cut groove 63. In oneembodiment, the end of the insulating coating layer 44 in the windingaxis direction may be located within the range of −2 mm to +2 mm withrespect to the lower end of the cut groove 63.

The plurality of segments 61 may form a plurality of segment groups fromthe core to the outer circumference. The plurality of segments belongingto the same segment group may be substantially the same as each other interms of at least one of a width, a height, and a separation pitch. Thewidth, height and separation pitch of segments belonging to the samesegment group may be the same as each other.

FIG. 7 b is a diagram showing the definitions of width (D), height (H)and separation pitch (P) of the trapezoidal segment 61.

Referring to FIG. 7 b , the width (D), height (H) and separation pitch(P) of the segment are designed to prevent abnormal deformation of theuncoated portion 43 while sufficiently increasing the number ofoverlapping layers in order to prevent the uncoated portion 43 near thebending point from being torn during bending of the uncoated portion 43and improve sufficient welding strength of the uncoated portion 43.

The segment 61 is bent on a line G passing through the lower end of cutgroove 63 or above the line G. The cut groove 63 may render bending ofthe segment 61 smooth and easy in a radial direction of the electrodeassembly.

The width (D) of the segment 61 is defined as a length between twopoints where two straight lines extending from both sides 63 b of thesegment 61 meet a straight line extending from the bottom portion 63 aof the cut groove 63. The height (H) of the segment 61 is defined as ashortest distance between the uppermost side of the segment 61 and astraight line extending from the bottom portion 63 a of the cut groove63. The separation pitch (P) of the segment 61 is defined as a lengthbetween two points where a straight line extending from the bottomportion 63 a of the cut groove 63 meets straight lines extending fromtwo sides 63 b connected to the bottom portion 63 a. When the side 63 band/or the bottom portion 63 a is curved, the straight line may bereplaced with a tangent line extending from the side 63 b and/or thebottom portion 63 a at the intersection point where the side 63 b andthe bottom portion 63 a meet.

Preferably, the width (D) of the segment 61 is at least 1 mm. If D isless than 1 mm, an area where the segment 61 does not overlap enough tosecure welding strength or an empty space (gap) may occur when thesegment 61 is bent toward the core.

Preferably, the width (D) of the segment 61 may be adaptively adjustedaccording to the radius of the winding turn where the segment 61 islocated so that the segment 61 easily overlaps in the radial directionwhen the segment 61 is bent toward the core of the electrode assembly.

FIG. 7 c is a diagram showing an arc (AIM formed by the lower end (linesegment Dab of FIG. 7 b ) of the segment 61 where the width (D) of thesegment 61 is defined when the electrode 60 is wound according to anembodiment of the present disclosure, based on the core center O of theelectrode assembly.

Referring to FIG. 7 c , the arc (A₁A₂) has a length corresponding to thewidth (D) of the segment 61, and has a circumferential angle (Φ) withrespect to the core center of the electrode assembly. Thecircumferential angle (Φ) may be defined as an angle between two linesegments connecting both ends of the arc (A₁A₂) and the core center O ona plane perpendicular to the winding axis passing through the arc(A₁A₂).

When the length of the arc (A₁A₂) of the segment 61 is the same, thecircumferential angle (Φ) decreases as the radius (r) of the windingturn where the segment 61 is located increases. Conversely, when thecircumferential angle (Φ) of the segment 61 is the same, as the radius(r) of the winding turn where the segment 61 is located increases, thelength of the arc (A₁A₂) increases proportionally.

The circumferential angle (Φ) affects the bending quality of the segment61. In the drawing, a solid arrow indicates a direction of a forceapplied to bend the segment 61, and a dotted arrow indicates a directionin which the segment 61 is bent. The bending direction is toward thecore center O.

The circumferential angle (Φ) of the segment 61 may be 45 degrees orless and more particularly 30 degrees or less depending on a radius (r)of a winding turn at which the segment is located, thereby to improvethe uniformity of bending and prevent cracks from occurring.

In one aspect, the circumferential angle (Φ) of the segment 61 mayincrease or decrease gradually or stepwise along a radial direction ofthe electrode assembly within the above numerical range. In otheraspect, the circumferential angle (Φ) of the segment 61 may increasegradually or stepwise and then decreases gradually or stepwise along aradial direction of the electrode assembly within the above numericalrange, or vice versa. In another aspect, the circumferential angle (Φ)of the segment 61 may be substantially the same along a radial directionof the electrode assembly within the above numerical range.

According to the experiment, when the circumferential angle (Φ) of thesegment 61 exceeds 45 degrees, the bending shape of the segment 61 isnot uniform. The force applied to a middle part of the segment 61 isseriously different from the force applied to a side part, so thesegment 61 is not uniformly pressed in the circumferential direction. Inaddition, if the pressing force is increased for the uniformity ofbending, there is a possibility that cracks may occur in the uncoatedportion 43 near the cut groove 63.

In one embodiment, the circumferential angle (Φ) of the segments 61included in the electrode 60 is substantially the same, and the width ofthe segment 61 may be proportionally increased as the radius (r) of thewinding turn where the segment 61 is located increases. The term‘substantially identical’ means that they are completely identical orthat there is a deviation of less than 5%.

For example, when the radius of the electrode assembly is 22 mm, theradius of the core is 4 mm, and the segment 61 starts to be disposedfrom the winding turn located at a point where the radius is 7 mm, ifthe circumferential angle (Φ) of the segments 61 is constant at 28.6degrees, the width (D) of the segment 61 may be proportionally increasedaccording to the radius (r) of the winding turn where the segment 61 islocated as shown in Table 1 below. That is, the width of the segment 61may be increased at substantially the same rate by 0.5 mm whenever theradius (r) of the winding turn increases by 1 mm.

TABLE 1 winding turn radius (mm) 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.015.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 segment width 3.5 4.0 4.5 5.05.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 (D, mm)circumferential 28.6 28.6 28.6 28.6 28.6 28.6 28.6 28.6 28.6 28.6 28.628.6 28.6 28.6 28.6 28.6 angle (degree)

Preferably, the width D(r) of the segment 61 located in a winding turnhaving a radius of r with respect to the core center O of the electrodeassembly may be determined in a range satisfying Formula 1 below.

1≤D(r)≤(2*π*r/360°)*45°  <Formula 1>

Preferably, each of the plurality of segments 61, as the radius (r) ofthe winding turn where the segment is located based on the core centerof the electrode assembly increases, the width D(r) in the windingdirection increases gradually or stepwise, or vice versa.

In another aspect, each of the plurality of segments 61, as the radius(r) of the winding turn where the segment is located based on the corecenter of the electrode assembly increases, the width D(r) in thewinding direction increases gradually or stepwise within the range of 1mm to 11 mm, or vice versa.

In another aspect, each of the plurality of segments 61, as the radius(r) of the winding turn where the segment is located based on the corecenter of the electrode assembly increases, the width D(r) in thewinding direction increases gradually or stepwise and then decreasegradually or stepwise, or vice versa.

In another aspect, each of the plurality of segments 61, as the radius(r) of the winding turn where the segment is located based on the corecenter of the electrode assembly increases, the width D(r) in thewinding direction increases gradually or stepwise and then decreasegradually or stepwise within the range of 1 mm to 11 mm, or vice versa.

In another aspect, a variation ratio of D(r), as the radius (r) of thewinding turn where the segment is located based on the core center ofthe electrode assembly increases, may be substantially the same ordifferent depending on the radius (r).

In another aspect, a variation ratio of D(r), as the radius (r) of thewinding turn where the segment is located based on the core center ofthe electrode assembly increases, may be substantially the same ordifferent depending on the radius (r), within the range of 1 mm to 11mm.

Referring to FIG. 7 b again, the height (H) of the segment 61 may be 2mm or more. If D2 is less than 2 mm, an area where the segment 61 doesnot overlap enough to secure welding strength or an empty space (gap)may occur when the segment 61 is bent toward the core.

The height (H) of the segment 61 may be determined by applying thecondition that the segment 61 does not cover the core when being benttoward the core. Preferably, the height (H) of the segment 61 may beadjusted so that the core may be opened to the outside by 90% or more ofits diameter.

Preferably, the height (H) of the segment 61 may gradually increase fromthe core to the outer circumference depending on the radius of the coreand the radius of the winding turn where the segment 61 is located.

In one embodiment, assuming that the height (H) of the segment 61increases stepwise over N steps from h₁ to h_(N) as the radius of thewinding turn increases, when a k^(th) height of the segment 61 is h_(k)(k is a natural number of 1 to N), a start radius of the winding turnincluding the segment 61 having the height h_(k) is r_(k), and theradius of the core is r_(c), the height h₁ to h_(N) of the segment 61may be determined to satisfy Formula 2 below.

2 mm≤h_(k)≤r_(k)−α*r_(c)(p referably, α is 0.90 to 1)  <Formula 2>

If the height (h_(k)) of the segment 61 satisfies Formula 2, even if thesegment 61 is bent toward the core, 90% or more of the diameter of thecore may be opened to the outside.

In one example, the total winding turn radius of the electrode 60 is 22mm, the height of the segment 61 starts from 3 mm, the height of thesegment 61 increases sequentially to 3 mm, 4 mm, 5 mm, and 6 mm wheneverthe radius of the winding turn including the segment 61 increases by 1mm, and the height of the segment 61 may be kept substantially the sameat 6 mm in the remaining winding turn. That is, among the radii of allwinding turns, the radial direction width of a height variable region ofthe segment 61 is 3 mm, and the remaining radial region corresponds to aheight uniform region.

In this case, according to the radius (r_(c)) of the core of theelectrode assembly, the start radius r₁, r₂, r₃, r₄ of the winding turnincluding the segment 61 with the height of 3 mm, 4 mm, 5 mm and 6 mmmay be as shown in Table 2 below, when a is 1 and the equal signcondition is applied in a right inequation of the above formula.

TABLE 2 segment height (mm) Item 3 (h₁) 4 (h₂) 5 (h₃) 6 (h₄) core 2 5(r₁) 6 (r₂) 7 (r₃) 8 (r₄) radius 2.5 5.5 (r₁)   6.5 (r₂)   7.5 (r₃)  8.5 (r₄)   (r_(c)) 3 6 (r₁) 7 (r₂) 8 (r₃) 9 (r₄) (mm) 3.5 6.5 (r₁)   7.5(r₂)   8.5 (r₃)   9.5 (r₄)   4 7 (r₁) 8 (r₂) 9 (r₃) 10 (r₄) 

When the segment 61 is disposed at the radial location shown in Table 2,the core is not covered by the segment 61 even if the segment 61 is benttoward the core. Meanwhile, r₁, r₂, r₃, r₄ shown in Table 2 may beshifted toward the core according to a value. In one example, when α is0.90, r₁, r₂, r₃, r₄ may be shifted toward the core by 10% of the coreradius. In this case, when the segment 61 is bent toward the core, 10%of the core radius is covered by the segment 61. r₁, r₂, r₃, r₄ shown inTable 2 are limit values of the location where the segment 61 starts.Accordingly, the location of the segment 61 may be shifted by apredetermined distance to the outer circumference further to the radiusshown in Table 1.

FIG. 7 d is a diagram schematically illustrating the relationshipbetween the heights h₁, h₂, h₃, h₄ of the segment, the core radius(r_(c)), and the radius r₁, r₂, r₃, r₄ of the winding turn at which thesegment 61 begins to appear.

Referring to Table 2 and FIG. 7 d together, for example, when the radius(r_(c)) of the core C is 3 mm, the start radius r₁, r₂, r₃ and r₄ of thewinding turn including the segment 61 having the height of 3 mm (h₁), 4mm (h₂), 5 mm (h₃) and 6 mm (h₄) may 6 mm, 7 mm, 8 mm and 9 mm,respectively, and the height of the segment 61 may be maintained as 6 mmfrom the radius of 9 mm to the last winding turn. Also, a winding turnhaving a radius less than 6 mm (r₁) may not include the segment 61. Inthis example, since the segment 61 of height 3 mm (h₁) closest to thecore C is located from the winding turn having the radius of 6 mm, evenif the segment 61 is bent toward the core C, the segment 61 covers onlythe radial region of 3 mm to 6 mm, and the core C is substantially notshielded. According to the a value of Formula 2, the location of thesegment may be shifted toward the core C within 10% of the core radius(r_(c)).

In another aspect, a height of the segment 61, as the start radius (r)of the winding turn where the segment 61 is located based on the corecenter of the electrode assembly increases, may increase insubstantially the same rate or different rage depending on the radius(r).

Preferably, the height (H) of the segment 61 may satisfy Formula 2 andsimultaneously the maximum height of the segment may be limited.

FIG. 7 e is a conceptual diagram for determining the maximum value(h_(max)) for the height (H) of the segment 61 in the height variableregion of the segment 61.

Referring to FIG. 7 e , in the winding structure of the electrodeassembly, an electrode (E₁) including the segment 61 faces an electrode(E₂) of opposite polarity with the separator S interposed therebetweenin the radial direction. Both surfaces of the electrode (E₁) are coatedwith an active material layer (E_(1,active)), and both surfaces of theelectrode (E₂) are also coated with an active material layer(E_(2,active)). For electrical insulation, the end (S_(end)) of theseparator S may further extend outward by a length corresponding to theinsulation gap (W_(gap)) from the end (E_(2,end)) of the electrode (E₂).In addition, the end of the electrode (E₁) does not extend outwardfurther to the end of the electrode (E₂) for electrical insulation.Therefore, a region corresponding to the insulation gap (W_(gap)) shouldbe secured at the lower end of the uncoated portion 43. Also, when theelectrodes (E₁, E₂) and the separator S are wound, the end (S_(end)) ofthe separator S causes meandering. Therefore, in order for the segment61 to be exposed out of the separator S, a region (W_(margin,min))corresponding to the minimum meandering margin of the separator S shouldbe allocated to the uncoated portion 43. In addition, in order to cutthe segment 61, a minimum cut scrap margin (W_(scrap,min)) should beallocated to the end of the current collector foil. Therefore, themaximum height (h_(max)) of the segment 61 in the height variable regionof the segment 61 may be determined by Formula 3 below. In Formula 3,W_(foil) corresponds to the width of the current collector foil beforethe current collector foil is cut.

h_(max)=W_(foil)−W_(scrap,min)−W_(margin,min)−W_(gap)  <Formula 3>

Preferably, the insulation gap (W_(gap)) may be in the range of 0.2 mmto 6 mm when the first electrode is a positive electrode and in therange of 0.1 mm to 2 mm when the first electrode is a negativeelectrode.

Preferably, the minimum cut scrap margin (W_(scrap,min)) may be in therange of 1.5 mm to 8 mm. The minimum cut scrap margin (W_(scrap,min))may not be considered depending on the process of cutting the segment61. For example, the cut groove 63 may be formed such that the upperside of the segment 61 is coincided with that of the current collectorfoil. In this case, W_(scrap,min) of the formula 3 may be zero.

Preferably, the minimum meandering margin (W_(margin,min)) may be in therange of 0 to 1 mm.

In one example, the minimum cut scrap margin (W_(scrap,min)) may be 1.5mm, and the minimum meandering margin (W_(margin,min)) of the separatorS may be 0.5 mm. Under these conditions, when the width (W_(foil)) ofthe current collector foil before forming the segment 61 is 8 mm to 12mm and the insulation gap (W_(gap)) is 0.6 mm, 0.8 mm and 1.0 mm, theresult of calculating the maximum height (h_(max)) of the segment 61using Formula 3 is as shown in Table 3 below.

TABLE 3 separator ↔ negative electrode gap (mm) item 0.6 0.8 1 current 85.4 5.2 5 collector 9 6.4 6.2 6 foil width 10 7.4 7.2 7 (mm) 11 8.4 8.28 12 9.4 9.2 9

Considering Table 3, the maximum height (h_(max)) of the segment 61 inthe height variable region of the segment 61 may be set to 10 mm.Therefore, in the height variable region of the segment 61, the heightof the segment 61 satisfies Formula 2 and at the same time may beincreased stepwise or gradually along the radial direction of theelectrode assembly in the region of 2 mm to 10 mm.

Referring to FIG. 7 b again, the separation pitch (P) of the segment 61may be adjusted in the range of 0.05 to 1 mm. If the separation pitch(P) is less than 0.05 mm, cracks may occur in the uncoated portion 43near the lower end of the cut groove 63 due to stress when the electrodetravels in a winding process or the like. Meanwhile, if the separationpitch (P) exceeds 1 mm, an empty space (gap) or an area where thesegments 61 do not overlap with each other enough to sufficiently securethe welding strength may occur when the segment 61 is bent.

Meanwhile, when the current collector 41 of the electrode 60 is made ofaluminum, the separation pitch (P) is may be set to 0.5 mm or more. Whenthe separation pitch (P) is 0.5 mm or more, it is possible to preventcracks from occurring in the lower portion of the cut groove 63 even ifthe electrode 60 travels at a speed of 100 mm/sec or more under atension of 300 gf or more during the winding process or the like.

According to the experimental results, when the current collector 41 ofthe electrode 60 is an aluminum foil with a thickness of 15 μm and theseparation pitch (P) is 0.5 mm or more, cracks do not occur in the lowerportion of the cut groove 63 when the electrode 60 travels under theabove conditions.

As shown in FIG. 7 b , the cut groove 63 is interposed between twosegments 61 adjacent to each other in the winding direction X. The cutgroove 63 corresponds to the space created as the uncoated portion 43 isremoved. Preferably, the both ends of the lower portion of the cutgroove 63 has a round shape. That is, the cut groove 63 includes asubstantially flat bottom portion 63 a and a round portion 63 c. Theround portion 63 c connects the bottom portion 63 a and the side 63 b ofthe segment 61. In a modified example, the bottom portion 63 a of thecut groove may be replaced with an arc shape. In this case, the sides 63b of the segments 61 may be smoothly connected by the arc shape of thebottom portion 63 a.

The curvature radius of the round portion 63 c may be in the range of 0to 0.5 mm, more particularly in the range of 0 to 0.1 mm, or even moreparticularly in the range of 0.01 mm to 0.05 mm. When the curvatureradius of the round portion 63 c meets the above numerical range, it ispossible to prevent cracks from occurring in the lower portion of thecut groove 63 while the electrode 60 is traveling in the winding processor the like.

In the plurality of segments 61, a lower internal angle (θ) may increasefrom the core to the outer circumference. The lower internal angle (θ)is an angle between a straight line extending from the bottom portion 63a of the cut groove 63 and a straight line extending from the sideportion 53 b of the segment 61. When the segment 61 is symmetrical inthe left and right direction, the lower internal angles (θ) at the leftand right sides are substantially the same.

If the radius of the electrode assembly increases, the radius ofcurvature increases. If the lower internal angle (θ) of the segments 61increases as the radius of the electrode assembly increases, the stressgenerated in the radial and circumferential directions when the segment61 is bent may be relieved. In addition, if the lower internal angle (θ)increases, when the segment 61 is bent, its area overlapping with thesegment 61 located at an inner side and the number of overlapping layersalso increase together, thereby ensuring uniform welding strength in theradial and circumferential directions and forming the bending surfaceregion in a flat form.

Preferably, the lower internal angle (θ) may be determined by the radiusof the winding turn where the segment 61 is located and the width (D) ofthe segment 61.

FIG. 7 f is a schematic diagram for explaining a formula for determiningthe lower internal angle (θ) of the segment 61.

Referring to FIG. 7 f , the side of the segment 61 identically coincideswith a line segment AE and a line segment DE connecting the core center(E) with both endpoints A and D of a line segment AD corresponding tothe width (D) of the segment 61.

When the side of the segment 61 extends in the most ideal direction,assuming that line segment EF is approximately equal to the line segmentAE and the line segment DE, the lower internal angle (θ_(refer)) of thesegment 61 may be determined approximately from the width (D) of thesegment 61 and the radius (r) of the winding turn where the segment 61is located by using Formula 4 below.

$\begin{matrix}{\theta_{refer} = {\cos^{- 1}( \frac{0.5*D}{r} )}} & {< {{Formula}4} >}\end{matrix}$

The angle in Formula 4 is an ideal criterion angle for the lowerinternal angle (θ_(refer)) of the segment 61. Meanwhile, a separationpitch (P) exists between adjacent segments 61 located in the samewinding turn. The length of the separation pitch (P) is indicated by p.Since the separation pitch (P) exists between adjacent segments 61, atolerance may be given to the lower internal angle (θ) by 50% of theseparation pitch (P). That is, the width of the upper side BC of thesegment 61 may be increased by p/2 at maximum to the upper side B′C′.The lower internal angle (θ′) reflecting the tolerance may be expressedby Formula 5 below. The lower internal angle (θ_(refer)) is the idealcriterion angle ∠BAG, and the lower internal angle (θ′) is the angle∠B′AG′ that reflects the tolerance according to the separation pitch(P). In Formula 5, H corresponds to the height of the segment 61, and pcorresponds to the separation pitch.

$\begin{matrix}{\theta^{\prime} = {\tan^{- 1}( \frac{2*H*\tan\theta_{refer}}{{2*H} - {p*\tan\theta_{refer}}} )}} & {< {{Formula}5} >}\end{matrix}$

Preferably, the lower internal angle (θ) of the segment 61 located ateach winding turn of the electrode assembly may satisfy Formula 6 below.Then, when the segments 61 are bent toward the core center of theelectrode assembly, the segments 61 adjacent in the circumferentialdirection do not interfere with each other and be bent smoothly.

$\begin{matrix}{{\cos^{- 1}( \frac{0.5*D}{r} )} \leq \theta \leq {\tan^{- 1}( \frac{2*H*\tan\theta_{refer}}{{2*H} - {p*\tan\theta_{refer}}} )}} & {< {{Formula}6} >}\end{matrix}$

In one example, when the electrode 60 forms a winding structure with adiameter of 22 mm and a core radius of 4 mm, the lower internal angle ofthe segment 61 may be increased stepwise in the range of 60 degrees to85 degrees in the height variable region.

Meanwhile, the lower internal angles of the segment 61 at the left andright sides may be different from each other. Nonetheless, at least oneof the lower internal angles at the left and right sides of the segment61 may be designed to satisfy the formula 6.

Referring to FIG. 7 a again, the width (d_(B1)) of the first part B1 isdesigned so that the core of the electrode assembly is opened to theoutside by 90% or more based on the diameter of the core when thesegment 61 of the third part B2 is bent toward the core. The width(d_(B1)) of the first part B1 may increase in proportion to the bendinglength of segment 61 of Group 1. The bending length corresponds to alength from the bending point to the uppermost side of the segment 61.Preferably, when the electrode 60 is used to manufacture an electrodeassembly of a cylindrical battery having a form factor of 4680, thewidth (d_(B1)) of the first part B1 may be set as 180 mm to 350 mmaccording to the diameter of the core of the electrode assembly and theheight of the segment 61 included in Group 1.

The bending point of the segment 61 may be set at a line passing throughthe lower end of the cut groove 63 or at a point spaced upward from theline by a predetermined distance. When the segments 61 are bent towardthe core at a point spaced from the lower end of the cut groove 63 by apredetermined distance, the segments may overlap more easily in theradial direction. When the segments 61 are bent, a segment located at anouter side based on the center of the core presses a segment at an innerside. At this time, if the bending point is spaced from the lower end ofthe cut groove 63 by a predetermined distance, a segment at an innerside is pressed by a segment at an outer side in the winding axisdirection, so that the segments overlap better. Preferably, theseparation distance of the bending point may be 1 mm or less. Theminimum height of the segment 61 is 2 mm and thus a ratio of theseparation distance to the minimum height of the segment 61 may be 50%or less.

In one embodiment, the width of each segment group may be designed toconstitute the same winding turn of the electrode assembly. Here, thewinding turn may be counted based on the end of the first part B1 whenthe electrode 60 is in a wound state.

In another modified example, the width of each segment group may bedesigned to constitute at least one winding turn of the electrodeassembly.

In still another modification, the width and/or height and/or separationpitch of the segment 61 belonging to the same segment group may beincreased or decreased gradually and/or stepwise and/or irregularlywithin the group or between the adjacent groups.

Groups 1 to 8 are only an example of segment groups included in thethird part B2. The number of groups, the number of segments 61 includedin each group, and the width of each group may be adjusted desirably sothat the segments 61 overlap in multiple layers to disperse stress asmuch as possible during the bending process of the uncoated portion 43and sufficiently secure the welding strength with a current collector.

In another modification, the height of the second part B3 may bedecreased gradually or step by step, as in the first embodiment and thesecond embodiment.

In still another modification, the segment structure of the third partB2 is expandable to the second part B3 (see dotted line). In this case,the second part B3 may also include a plurality of segments like thethird part B2. Preferably, the segment structure of the second part B3may be substantially the same as the segment group at the outermost sideof the third part B2. In this case, the segments included in the secondpart B3 and the third part B2 may have substantially the same in termsof the width, height, and separation pitch. In a modification, thesegment of the second part B3 may have a width and/or height and/orseparation pitch greater than that of the third part B2.

In third part B2, the region (Groups 1 to 7) in which the height of thesegment 61 increases stepwise based on the winding direction of theelectrode 60 is defined as a height variable region of the segment, andthe segment group at the last (Group 8) may be defined as a heightuniform region in which the height of the segment is maintaineduniformly.

That is, in the third part B2, when the height of the segment 61 isgradually increased from h₁ to h_(N), the region in which segments 61having a height of h₁ to h_(N-1) (N is height index and a natural numberof 2 or above) is arranged corresponds to a height variable region, andthe region in which segments 61 having a height of h_(N) are arrangedcorresponds to a height uniform region. The ratio of the height variableregion and the height uniform region to the length of the electrode 60in the winding direction will be described later with reference tospecific embodiments.

When the electrode plate 60 is used to manufacture an electrode assemblyof a cylindrical battery having a form factor of 4680, the width(d_(B1)) of the first part B1 may be 180 to 350 mm. The width of Group 1may be 35 to 40% of the width of the first part B1. The width of Group 2may be 130 to 150% of the width of Group 1. The width of Group 3 may be120 to 135% of the width of Group 2. The width of group 4 may be 85 to90% of the width of group 3. The width of Group 5 may be 120 to 130% ofthe width of Group 4. The width of Group 6 may be 100 to 120% of thewidth of Group 5. The width of Group 7 may be 90 to 120% of the width ofGroup 6. The width of Group 8 may be 115 to 130% of the width of Group7. The width (d_(B3)) of the second part B3 may be 180 to 350 mm, likethe width of the first part B1.

The reason that the widths of Groups 1 to 8 do not show a constantincrease or decrease pattern is that the segment width graduallyincreases from Group 1 to Group 8, but the number of segments includedin the group is limited to an integer number and the thickness of theelectrode has slight deviation along a winding direction. Accordingly,the number of segments may be reduced in a specific segment group.Therefore, the widths of the groups may show an irregular change patternas in the above example from the core to the outer circumference.

That is, assuming that the width in the winding direction for each ofthe three segment groups consecutively adjacent to each other in thecircumferential direction of the electrode assembly is W1, W2, and W3,respectively, it is possible to include a combination of segment groupsin which W3/W2 is smaller than W2/W1.

In the specific example, Groups 4 to 6 corresponds to the above case.The width ratio of Group 5 to Group 4 is 120 to 130%, and the widthratio of Group 6 to Group 5 is 100 to 120%, which is smaller than 120 to130%.

According to another modification, when the uncoated portion 43 of theelectrode 60 has a segment structure, the electrode 60 may include asegment skip region 64 in which some of the plurality of segments areregularly or irregularly omitted as shown in FIG. 7 g.

Preferably, the segment skip region 64 may be provided in plural. In anexample, the width of the segment skip region 64 may be constant fromthe core toward the outer circumference. In another example, the widthof the segment skip region 64 may increase or decrease regularly orirregularly from the core toward the outer circumference. Preferably,the height of the uncoated portion existing in the segment skip region64 may correspond to the height of the first part B1 and/or the secondpart B3.

The number of segments 61 existing between the segment skip regions 64may be at least one. As shown in FIG. 7 g , the electrode 60 may includean uncoated portion in which the number of segments 61 existing betweenthe segment skip regions 64 increases from the core toward the outercircumference.

Preferably, the width of the segment skip region 64 may be set such thatwhen the electrode 60 is wound as shown in FIG. 7 h , segments locatedin each winding turn may be located in a preset independent region 66with respect to the core center C of the electrode assembly 65.

That is, the plurality of segments 61 may be located within a pluralityof independent regions 66 with respect to the core center C when theelectrode assembly 65 is viewed in the winding axis direction. Thenumber of independent regions 66 may be changed to 2, 3, 4, 5, or thelike.

Preferably, the independent region 66 may have a sectoral shape. In thiscase, the angle between the independent regions 66 may be substantiallythe same. In addition, the circumferential angle (δ) of the independentregion 66 may be 20 degrees or more, optionally 25 degrees or more,optionally 30 degrees or more, optionally 35 degrees or more, oroptionally 40 degrees or more.

In a modified example, the independent region 66 may have a geometricshape such as a square, a rectangle, a parallelogram, a trapezoidal, orthe like.

In the present disclosure, the shape of the segment 61 may be variouslymodified.

FIG. 8 a is a plan view showing the structure of an electrode 70according to the fifth embodiment of the present disclosure.

Referring to FIG. 8 a , the electrode 70 of the fifth embodiment hassubstantially the same configuration as that of the former embodiment,except that the shape of the segment 61′ is different. Therefore, unlessotherwise stated, the configuration of the fourth embodiment may beequally applied to the fifth embodiment.

The segment 61′ has a geometric shape with substantially the same widthat the top and bottom. Preferably, the segment 61′ may have arectangular shape.

FIG. 8 b is a diagram showing the definition of the width, height, andseparation pitch of the rectangular segment 61′.

Referring to FIG. 8 b , the width (D), height (H) and separation pitch(P) of the segment 61′ may be set to prevent the uncoated portion 43from being abnormally deformed while sufficiently increasing the numberof overlapping layers of the uncoated portion 43, in order to preventthe uncoated portion 43 from being torn while bending the uncoatedportion 43 and improve the welding strength with a current collector.The abnormal deformation means that the uncoated portion below thebending point does not maintain a straight line state and is collapsedand deformed irregularly.

The width (D) of the segment 61′ is defined as a length between twopoints where two straight lines extending from both sides of the segment61′ meet a straight line extending from the bottom portion 63 a of thecut groove 63. The height (H) of the segment 61′ is defined as ashortest distance between the uppermost side of the segment 61′ and thestraight line extending from the bottom portion 63 a of the cut groove63. The separation pitch (P) of the segment 61′ is defined as a lengthbetween two points where the straight line extending from the bottomportion 63 a of the cut groove 63 meets straight lines extending fromtwo sides 63 b connected to the bottom portion 63 a. When the side 63 band/or the bottom portion 63 a is curved, the straight line may bereplaced with a tangent line extending from the side 63 b and/or thebottom portion 63 a at the intersection point where the side 63 b andthe bottom portion 63 a meet.

Preferably, the conditions regarding the width (D), height (H), andseparation pitch (P) of the segment 61′ are substantially the same asthose of the fourth embodiment, and thus will not be described again.However, since the segment 61′ has a rectangular shape, the lowerinternal angle of the segment 61′ may be constant at 90 degrees.

Similar to the electrode 60 of the fourth embodiment, the electrode 70according to the fifth embodiment may also include a segment skip region64 in which some of the plurality of segments are regularly orirregularly omitted as shown in FIG. 8 c.

In addition, when the electrode 70 including the segment skip region 64is wound into an electrode assembly, the segments may be located withina plurality of independent regions 66 as shown in FIG. 7 h.

As in the fourth embodiment and the fifth embodiment, when the thirdpart B2 and the second part B3 include a plurality of segments 61, 61′,the shape of each segment 61, 61′ may be variously modified.

Preferably, the segment may be deformed into various shapes whilesatisfying at least one of the following conditions.

Condition 1: The width of the lower portion is greater than the width ofthe upper part.

Condition 2: The width of the lower portion and the width of the upperpart are the same.

Condition 3: The width remains the same from the bottom to the top.

Condition 4: The width decreases from bottom to top.

Condition 5: The width decreases and then increases from bottom to top.

Condition 6: The width increases and then decreases from bottom to top.

Condition 7: The width increases from the bottom to the top and remainsconstant.

Condition 8: The width decreases from the bottom to the top and remainsconstant.

Condition 9: The internal angle of one side of the lower portion and theinternal angle of the other side are the same

Here, the internal angle may be defined as an angle formed by the sideportion of the segment based on the width direction of the lower portionof the segment. When the side portion is curved, the internal angle isdefined as an angle between a tangent line drawn at the lowest end ofthe curve and the width direction of the lower portion of the segment.

Condition 10: The internal angle of one side of the lower portion andthe internal angle of the other side are different from each other.

Condition 11: The internal angle of one side of the lower portion andthe internal angle of the other side of the lower portion have an acuteangle, a right angle, or an obtuse angle, respectively.

Condition 12: Left and right symmetrical with respect to the windingaxis direction.

Condition 13: Left and right asymmetrical with respect to winding axisdirection.

Condition 14: The side portion has a straight line shape.

Condition 15: The side portion is curved.

Condition 16: The side portion is outwardly convex.

Condition 17: The side portion is inwardly convex.

Condition 18: The corner of the upper portion and/or the lower portionhas a structure where a straight line meets a straight line.

Condition 19: The corner of the upper portion and/or the lower portionhas a structure where a straight line meets a curve.

Condition 20: The corner of the upper portion and/or the lower portionhas a structure where a curve meets a curve

Condition 21: The corner of the upper portion and/or the lower portionhas a round structure.

FIG. 9 is a diagram exemplarily showing the shapes of segments accordingto modified examples of the present disclosure.

As shown in the drawing, the segment may have various geometric shapesin which a dotted line connecting the bottom portions of the cut groovesat both sides is the base. The geometric figure has a structure in whichone or more straight lines, one or more curves, or a combination thereofis connected. In one example, the segment may have a polygonal shape, around shape, or various shapes combined therewith.

Specifically, the segment may have a left-right symmetric trapezoidalshape ({circle around (a)}); a left-right asymmetric trapezoidal shape({circle around (b)}); a parallelogram shape ({circle around (c)}); atriangular shape ({circle around (1)}); a pentagonal shape ({circlearound (k)}); an arc shape ({circle around (e)}); or a semiellipticalshape ({circle around (f)}).

Since the shape of the segment is not limited to those shown in FIG. 9 ,it may be transformed into other polygonal shapes, other round shapes,or a combination thereof so as to satisfy at least one of Conditions 1to 21 described above.

In the polygonal shapes {circle around (a)}, {circle around (b)},{circle around (c)}, {circle around (k)} and {circle around (l)} of thesegment, the corner of the upper portion and/or the lower portion may bea shape where a straight line meets a straight line, or a round shape(see the enlarged view of the corner of the upper portion and the lowerportion of the shape {circle around (a)}).

In the polygonal shapes {circle around (a)}, {circle around (b)},{circle around (c)}, {circle around (k)} and {circle around (l)} of thesegment and the curve shapes {circle around (e)} and {circle around (f)}of the segment, the internal angle (θ₁) at one side of the lower portionand the internal angle (θ₂) at the other side thereof may be the same ordifferent from each other, and the internal angle (θ₁) at one side ofthe lower portion and the internal angle (θ₂) at the other side thereofmay be any one of an acute angle, a right angle, or an obtuse angle,respectively. The internal angle is an angle where the base and the sideof a geometric figure meet. When the side is a curve, the straight linemay be replaced by a tangent line extending at a point where the baseand the side meet.

The shape of the side portion of the segment having a polygonal shapemay be modified in various ways.

In one example, the side portion of the segment shape {circle around(a)} may be transformed into an outwardly convex curve as in the shape{circle around (d)} or into a curve recessed into the segment as in theshape {circle around (g)} or {circle around (j)}.

In another example, the side portion of the segment shape {circle around(a)} may be transformed into a bent straight line recessed into thesegment as in the shape {circle around (h)} or {circle around (i)}. Theside portion of the segment shape {circle around (a)} may be transformedinto a bent straight line convex outwardly.

In the segment shapes {circle around (d)}, {circle around (g)}, {circlearound (j)}, {circle around (h)} and {circle around (i)} in which theside portion is variously modified, the internal angle (θ₁) at one sideof the lower portion and the internal angle (θ₂) at the other sidethereof may be the same or different from each other, and the internalangle (θ₁) of one side of the lower portion and the internal angle (θ₂)at the other side thereof may be any one of an acute angle, a rightangle, or an obtuse angle, respectively.

The width of the segment may have various change patterns from thebottom to the top.

In one example, the width of the segment may be kept constant from thebottom to the top (shape {circle around (c)}). In another example, thewidth of the segment may gradually decrease from the bottom to the top(shapes {circle around (a)}, {circle around (b)}, {circle around (d)},{circle around (e)}, {circle around (f)}, and {circle around (g)}). Instill another example, the width of the segment may gradually decreaseand then increase from the bottom to the top (shape {circle around (i)}and {circle around (j)}). In still another example, the width of thesegment may gradually increase from the bottom to the top and thendecrease (shape {circle around (k)}). In still another example, thewidth of the segment may gradually decrease from the bottom to the topand then be maintained constant (shape {circle around (h)}). The widthof the segment may gradually increase from the bottom to the top and bemaintained constant (shape {circle around (m)}).

Meanwhile, among the shapes of the segments shown in FIG. 9 , apolygonal shape with a flat top may be rotated by 180 degrees. In oneexample, when the segment shape {circle around (a)}, {circle around(b)}, {circle around (d)} or {circle around (g)} is rotated by 180degrees, the width of the segment may gradually increase from the bottomto the top. In another example, if the segment shape {circle around (h)}is rotated by 180 degrees, the width of the segment may be kept constantfrom the bottom to the top and then gradually increase.

In the above embodiments (modifications), according to another aspect ofthe present disclosure, it is possible to change the shapes of thesegments 61, 61′ differently depending on the region of the third partB2. In one example, a round shape (e.g., semicircle, semielliptical,etc.) that is advantageous for stress distribution is applied to aregion where the stress is concentrated, and a polygonal shape (e.g., arectangle, trapezoid, parallelogram, etc.) with the largest area may beapplied a region where the stress is relatively low.

In the above embodiments (modifications), the segment structure of thethird part B2 may also be applied to the first part B1. However, if thesegment structure is applied to the first part B1, when the segments 61,61′ of the third part B2 are bent according to the radius of curvatureof the core, the end of the first part B1 may be bent toward the outercircumference, which is called reverse forming. Therefore, the firstpart B1 has no segment, or even if the segment structure is applied tothe first part B1, it is desirable to control the width and/or heightand/or separation pitch of the segments 61, 61′ as small as possible inconsideration of the radius of curvature of the core such that reverseforming does not occur.

According to still another aspect of the present disclosure, after theelectrode 60, 70 is wound into an electrode assembly, the segmentsexposed at the upper and lower portions of the electrode assembly may beoverlapped into multiple layers along the radial direction of theelectrode assembly to form a bending surface region.

FIG. 10 a is a schematic diagram showing a cross section of the bendingsurface region F formed as the segment 61 is bent toward the core C ofthe electrode assembly 80. In FIG. 10 a , only on a left side of thecross section of the bending surface region F is shown with respect tothe winding axis of the electrode assembly 80. The bending surfaceregion F may be formed at both the upper and lower portions of theelectrode assembly 80. FIG. 10 b is a top perspective view schematicallyshowing the electrode assembly 80 at which the bending surface region Fis formed.

Referring to FIGS. 10 a and 10 b , the bending surface region F has astructure in which the segments 61 are overlapped into multiple layersin the winding axis direction. The overlapping direction is the windingaxis direction (Y). Region {circle around (1)} is a segment skip region(the first part B1) having no segment, and Regions {circle around (2)}and {circle around (3)} are regions where the winding turn including thesegment 61 is located. Region {circle around (2)} is a height variableregion in which the height of the segment 61 is variable, and Region{circle around (3)} is a height uniform region in which the height ofthe segment is maintained uniformly to the outer circumference of theelectrode assembly. As will be described later, the radial lengths ofRegion {circle around (2)} and Region {circle around (3)} may bevariable. Meanwhile, the uncoated portion (the second part B3) includedin at least one winding turn including the outermost winding turn maynot include a segment structure. In this case, the second part B3 may beexcluded from Region {circle around (3)}.

In Region {circle around (2)}, the heights of the segments 61 may bechanged stepwise from the minimum height h₁ (=h_(min)) to the maximumheight h_(N) (=h_(max)) in the radius region of r₁ to r_(N) of theelectrode assembly 80. The height variable region in which the heightsof segments 61 are variable is r₁ to r_(N). From the radius r_(N) to theradius R of the electrode assembly 80, the heights of the segments 61are uniformly maintained at h_(N). Uniform height means that the heightdeviation is within 5%.

At any radial location of Region {circle around (2)} and Region {circlearound (3)}, the number of overlapping layers of the segments 61 variesdepending on the radial location. In addition, the number of overlappinglayers of the segments 61 may vary based on the width of Region {circlearound (2)}, the minimum height (h₁) and the maximum height (h_(N-1)) ofthe segments in the height variable region of the segment 61, and theheight change amount (Δh) of the segments 61. The number of overlappinglayers of the segments 61 is the number of segments that meet a virtualline when the virtual line is drawn in the winding axis direction at anyradial location of the electrode assembly 80.

Preferably, the number of overlapping layers of the segments 61 at eachposition of the bending surface region F may be optimized suitable forthe required welding strength of the current collector by adjusting theheight, width and separation pitch of the segment 61 according to theradius of the winding turn including the segment 61.

First, when the minimum height (h₁) of the segment is the same in theheight variable region ({circle around (2)}) of the segment 61, it willbe described through specific examples how the number of overlappinglayers of the segments 61 is changed along the radial direction of thebending surface region F according to the change in the maximum height(h_(N)) of the segment 61.

The electrode assemblies of Examples 1-1 to 1-7 are prepared. Theelectrode assemblies of these examples have a radius of 22 mm and a corediameter of 4 mm. The positive electrode and the negative electrodeincluded in the electrode assembly have the electrode structure shown inFIG. 7 a . That is, the segment has a trapezoidal shape. The second partB3 of the positive electrode and the negative electrode has no segment.The length of the second part B3 is 2% to 4% compared to the totallength of the electrode. The positive electrode, the negative electrodeand the separator are wound by the method described with reference toFIG. 2 . The winding turns are between 48 turns and 56 turns, whereasthe winding turns of these examples are 51 turns. The thicknesses of thepositive electrode, the negative electrode and the separator are 149 μm,193 μm, and 13 μm, respectively. The thickness of the positive electrodeand the negative electrode is the thickness including the thickness ofthe active material layer. The thickness of the positive electrodecurrent collecting plate and the negative electrode current collectingplate are 15 μm and 10 μm, respectively. The lengths of the positiveelectrode and the negative electrode in the winding direction are 3948mm and 4045 mm, respectively.

In each example, the minimum height of the segment 61 is set to 3 mm sothat the height variable region ({circle around (2)}) of the segment 61starts from a radius of 5 mm. Also, in each example, the height of thesegment 61 is increased by 1 mm for every 1 mm increase in radius, andthe maximum height of the segment 61 is changed variously from 4 mm to10 mm.

Specifically, in Example 1-1, the height variable region ({circle around(2)}) of the segment 61 is 5 mm to 6 mm, and the height of the segment61 is variable at a radius from 3 mm to 4 mm. In Example 1-2, the heightvariable region ({circle around (2)}) of the segment 61 is 5 mm to 7 mm,and the height of the segment 61 is variable from 3 mm to 5 mm. InExample 1-3, the height variable region ({circle around (2)}) of thesegment 61 is 5 mm to 8 mm, and the height of the segment 61 is variablefrom 3 mm to 6 mm. In Example 1-4, the height variable region ({circlearound (2)}) of the segment 61 is 5 mm to 9 mm, and the height of thesegment 61 is variable from 3 mm to 7 mm. In Example 1-5, the heightvariable region ({circle around (2)}) of the segment 61 is 5 mm to 10mm, and the height of the segment 61 is variable from 3 mm to 8 mm. InExample 1-6, the height variable region ({circle around (2)}) of thesegment 61 is 5 mm to 11 mm, and the height of the segment 61 isvariable from 3 mm to 9 mm. In Example 1-7, the height variable region({circle around (2)}) of the segment 61 is 5 mm to 12 mm, and the heightof the segment 61 is variable from 3 mm to 10 mm. In Examples 1-1 to1-7, the height of the segment is uniform from the radius correspondingto the upper limit of the height variable region ({circle around (2)})to the outer circumference. In one example, in Example 1-7, the heightof the segment 61 located at a radius from 12 mm to 22 mm is uniform as10 mm. Meanwhile, in the electrode assembly of the comparative example,the height of segment 61 is maintained at a single height of 3 mm fromthe radius of 5 mm to the radius of 22 mm.

FIG. 10 c is a graph showing the results of counting the number ofoverlapping layers of the segments along the radial direction in thebending surface region F of the positive electrode formed on the upperportion of the electrode assemblies according to Examples 1-1 to 1-7 andthe comparative example. The bending surface region of the negativeelectrode shows substantially the same result. The horizontal axis ofthe graph is the radius based on the core center, and the vertical axisof the graph is the number of overlapping layers counted at each radiuspoint, and it is the same in FIGS. 10 d and 10 e , which will beexplained later.

Referring to FIG. 10 c , the overlapping layer number uniform region b1of the segment is commonly shown in Examples 1-1 to 1-7 and thecomparative example 1. The overlapping layer number uniform region b1 isa radial region of a flat region in each graph. The length of theoverlapping layer number uniform region b1 increases as the maximumheight of the segment decreases, and the overlapping layer numberuniform region (b1′) of the comparative example is longest. Meanwhile,the number of overlapping layers of the segments increases as themaximum height (h^(N)) of the segment increases. That is, if the maximumheight (h^(N)) of the segment increases so that the width of the heightvariable region ({circle around (2)}) of the segment increases, thenumber of overlapping layers of the segments increases, but the width ofthe overlapping layer number uniform region b1 decreases. At an outerside of overlapping layer number uniform region b1, the overlappinglayer number decreasing region b2 appears, in which the number ofoverlapping layers decreases as the radius increases. The overlappinglayer number decreasing region b2 is a radial region where the number ofoverlapping layers decreases as the radius of the electrode assemblyincreases. The overlapping layer number uniform region b1 and theoverlapping layer number decreasing region b2 are adjacent in the radialdirection and are complementary to each other. That is, if the length ofone region increases, the length of the other region decreases. Inaddition, the amount of decrease in the number of overlapping layers inthe overlapping layer number decreasing region b2 is proportional to thedistance spaced apart from the overlapping layer number uniform regionb1.

From the viewpoint of the number of overlapping layers of the segments,in Examples 1-1 to 1-7, the number of overlapping layers of the segmentsis 10 or more in the overlapping layer number uniform region b1. Aregion in which the number of overlapping layers of segments is or moremay be set as a welding target region. The welding target region is aregion where at least a part of the current collector can be welded.

In Examples 1-1 to 1-7, the overlapping layer number uniform region b1starts from a radius point where the height variable region ({circlearound (2)}) of the segment starts. That is, the height variable region({circle around (2)}) starts from the radius of 5 mm and extends towardthe outer circumference.

Table 4 below shows, in Examples 1-1 to 1-7 and comparative example 1,for the positive electrode, calculation results of a ratio of the lengthof the segment skip region (c, {circle around (1)} in FIG. 10 a ) to theradius (b-a) of the electrode assembly excluding the core, a ratio (e/f)of the length of the overlapping layer number uniform region b1 to thelength (f) from the radius point (5 mm) where the overlapping layernumber uniform region starts to an outermost point of the electrodeassembly (22 mm), a ratio (d/f) of the length of the height variableregion (d) of the segment (d) to the length (f) from the radius point (5mm) where the overlapping layer number uniform region starts to theoutermost point (22 mm) of the electrode assembly, a ratio (h) of thelength of the electrode area corresponding to the segment skip region(first part B1) to the total length of the electrode, a ratio (i) of thelength of the electrode area corresponding to the height variable regionto the total length of the electrode, a ratio (j) of the electrode areacorresponding to the height uniform region to total length of theelectrode, and the like.

Except that the negative electrode shows a difference of 0.1 to 1.2%with respect to the parameter h, the remaining parameters aresubstantially the same as the positive electrode. The sum of proportionsh, i and j is slightly different from 100%. The reason is that there isa region having no segment in the second part B3 corresponding to theouter circumferential uncoated portion of the electrode. For example, inExample 1-1, there is no segment in the second part B3 corresponding toapproximately 4% of the total electrode length. In Table 4, a to f areparameters based on the length in the radial direction, and h, i and jare parameters based on the length in the lengthwise direction of theelectrode before being wound into an electrode assembly. In addition,the parameters corresponding to the ratio (%) are values rounded to thefirst decimal place. These points are substantially the same in Tables 5and 6, explained later.

TABLE 4 e. b. c. d. overlapping h. i. j. a. winding segment height layernumber f. g. ratio of ratio of ratio of core structure skip variableuniform segment number of segment height height radius radius regionregion region region overlapping c/(b − a) d/f e/f skip variable uniformRef. (mm) (mm) (mm) (mm) (mm) (mm) layers (%) (%) (%) region regionregion Example 2 22 3 1 14 17 11 15%  6% 82% 6%  3% 87% 1-1 Example 2 223 2 13 17 13 15% 12% 76% 6%  7% 83% 1-2 Example 2 22 3 3 12 17 16 15%18% 71% 6% 11% 80% 1-3 Example 2 22 3 4 11 17 18 15% 24% 65% 6% 15% 75%1-4 Example 2 22 3 5 10 17 21 15% 29% 59% 6% 21% 69% 1-5 Example 2 22 36 9 17 24 15% 35% 53% 6% 25% 65% 1-6 Example 2 22 3 7 8 17 26 15% 41%47% 6% 32% 59% 1-7 Comparative 2 22 3 0 15 17 8 15%  0% 88% 6% — —Example 1

Seeing Example 1-1 to 1-7 of Table 4, the number of overlapping layersof the segments is 11 to 26, and the ratio (d/f) of the height variableregion (d) to the radius region (f) including the segment is 6% to 41%.In addition, the ratio (e/f) of the overlapping layer number uniformregion (e) to the radius region (f) including the segment is 47% to 82%.In addition, the ratio (c/(b-a)) of the segment skip region (c, {circlearound (1)} in FIG. 10 a ) to the radius (b-a) of the electrode assemblyexcluding the core is 15%. In addition, the ratio of the length of theelectrode area corresponding to the segment skip region (first part B1)to the total length of the electrode is 6%, the ratio of the length ofthe electrode area corresponding to the height variable region to thetotal length of the electrode is 3% to 32%, and the ratio of the lengthof the electrode area corresponding to the height uniform region to thetotal length of the electrode is 59% to 87%.

The number of overlapping layers (g) of the overlapping layer numberuniform region is or more for all of Examples 1-1 to 1-7. Theoverlapping layer number uniform region (e) decreases as the heightvariable region (d) of the segment increases, but the number ofoverlapping layers (g) of the segments increases in the overlappinglayer number uniform region (e). Preferably, the overlapping layernumber uniform region (e) in which the number of overlapping layers (g)of the segments is 10 or more may be set as a welding target region.

In the cylindrical battery with form factors of 1865 and 2170, theradius of the electrode assembly is approximately 9 mm to 10 mm.Therefore, for a conventional cylindrical battery, the radial length ofthe segment region (f) cannot be secured at the level of 17 mm as inExamples 1-1 to 1-7, and the length of the overlapping layer numberuniform region (e) in which the number of overlapping layers of thesegments is 10 or more cannot be secured at the level of 8 mm to 14 mm.This is because, in the conventional cylindrical battery, when theradius of the core is designed to be 2 mm, which is the same as inExamples 1-1 to 1-7, the radial region in which the segments can bedisposed is substantially only 7 mm to 8 mm. In addition, in theconventional cylindrical battery, the length of the electrode in thewinding direction is in the level of 600 mm to 980 mm. Such a shortelectrode length is only about 15% to 24% of the length of the electrodeused in Examples 1-1 to 1-7 (the positive electrode of 3948 mm, thenegative electrode of 4045 mm). Accordingly, the numerical ranges forthe parameters h, i and j cannot be easily derived from the designspecifications of the conventional cylindrical battery.

Next, it will be explained through concrete examples how the number ofoverlapping layers of the segments changes in the radial direction ofthe bending surface region F according to the change in the minimumheight (h₁) of the segment when the maximum height (h_(N)) of thesegment is the same in the height variable region of the segment({circle around (2)} in FIG. 10 a ).

The electrode assemblies of Examples 2-1 to 2-5 has a radius of 22 mm,and the core C has a diameter of 4 mm. In the height variable region ofthe segment 61 (0 in FIG. 10 a ), the minimum height (h₁) is the same as4 mm, and the maximum height (h_(N)) is changed from 6 mm to 10 mm by 1mm. Therefore, in the electrode assemblies of Examples 2-1 to 2-5, thewidth of the height variable region ({circle around (2)} in FIG. 10 a )of the segment is 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, respectively, andthe segment skip region ({circle around (1)} of FIG. 10 a ) is a radialregion having a radius from 2 mm to 6 mm.

The electrode assemblies Examples 3-1 to 3-4 have radius of 22 mm, andthe core C has a diameter of 4 mm. In the height variable region of({circle around (2)} of FIG. 10 a ) of the segment 61, the minimumheight (h₁) is the same as 5 mm, and the maximum height (h_(N)) ischanged from 7 mm to 10 mm by 1 mm. Therefore, in the electrodeassemblies of Examples 3-1 to 3-4, the width of the segment heightvariable region ({circle around (2)} in FIG. 10 a ) is 2 mm, 3 mm, 4 mm,and 5 mm, respectively, and the segment skip region ({circle around (1)}in FIG. 10 a ) is a radial region having a radius from 2 mm to 7 mm.

The electrode assemblies of Examples 4-1 to 4-3 have a radius of 22 mm,and the core C has a diameter of 4 mm. In the height variable region({circle around (2)} in FIG. 10 a ) of the segment 61, the minimumheight (h₁) is the same as 6 mm, and the maximum height (h) is changedfrom 8 mm to 10 mm by 1 mm. Therefore, in the electrode assemblies ofExamples 4-1 to 4-3, the width of the height variable region ({circlearound (2)} in FIG. 10 a ) of the segment is 2 mm, 3 mm, and 4 mm,respectively, and the segment skip region ({circle around (1)} in FIG.10 a ) is a radius region having a radius from 2 mm to 8 mm.

The electrode assemblies of Examples 5-1 to 5-2 have a radius of 22 mm,and the core C has a diameter of 4 mm. In the height variable region({circle around (2)} in FIG. 10 a ) of the segment 61, the minimumheight (h₁) is the same as 7 mm, and the maximum height (h_(N)) ischanged from 9 mm to 10 mm by 1 mm. Therefore, in the electrodeassemblies of Examples 5-1 to 5-2, the width of the height variableregion ({circle around (2)} in FIG. 10 a ) of the segment is 2 mm and 3mm, respectively, and the segment skip region ({circle around (1)} inFIG. 10 a ) is a radius region having a radius from 2 mm to 9 mm.

FIG. 10 d is graphs showing the results of counting the number ofoverlapping layers of segments measured along the radial direction inthe bending surface region F of the positive electrode formed on theupper portion of the electrode assemblies of Examples 2-1 to 2-5,Examples 3-1 to 3-4, Examples 4-1 to 4-3, and Examples 5-1 to 5-2. Thebending surface region of the negative electrode also showssubstantially the same results.

In FIG. 10 d , Graph (a) shows the result of counting the number ofoverlapping layers of the segments along the radial direction in thebending surface region F for Examples 2-1 to 2-5, Graph (b) shows theresult for Examples 3-1 to 3-4, Graph C shows the result for Examples4-1 to 4-3, and Graph (d) shows the result for Example 5-1 to Example5-2.

Referring to FIG. 10 d , the overlapping layer number uniform region b1of the segment appears in common in all examples. The overlapping layernumber uniform region b1 is a radial region of a flat region in thegraph. The length of the overlapping layer number uniform region b1increases as the maximum height (h_(N)) of the segment decreases whenthe minimum height (h₁) of the segment is the same. Also, the length ofthe overlapping layer number uniform region b1 increases as the minimumheight (h₁) of the segment decreases when the maximum height (h_(N)) ofthe segment is the same. Meanwhile, in the overlapping layer numberuniform region b1, the number of overlapping layers of the segmentsincreases as the maximum height (h_(N)) of the segment increases. Alsoin the examples, the overlapping layer number decreasing region b2appears adjacent to the overlapping layer number uniform region b1.

In the examples, the number of overlapping layers of the segments in theoverlapping layer number uniform region b1 is all 10 or more.Preferably, the region in which the number of overlapping layers ofsegments is 10 or more may be set as a welding target region.

In the examples, the overlapping layer number uniform region b1 startsfrom a radius point where the height variable region ({circle around(2)} in FIG. 10 a ) of the segment starts. In Examples 2-1 to 2-5, theheight variable region ({circle around (2)} in FIG. 10 a ) of thesegment starts from 6 mm and extends toward the outer circumference. InExamples 3-1 to 3-4, the height variable region ({circle around (2)} inFIG. 10 a ) of the segment starts from 7 mm and extends toward the outercircumference. In Examples 4-3 to 4-3, the height variable region({circle around (2)} in FIG. 10 a ) of the segment starts from 8 mm andextends toward the outer circumference. In Examples 5-1 to 5-2, theheight variable region ({circle around (2)} in FIG. 10 a ) of thesegment starts from 9 mm and extends toward the outer circumference.

Table 5 below shows the results of calculating various parameters suchas a ratio (e/f) of the length of the overlapping layer number uniformregion to the length from the radius point (6 mm, 7 mm, 8 mm, 9 mm)where the overlapping layer number uniform region starts to theoutermost point (22 mm) of the electrode assembly, a ratio (d/f) of thelength of the height variable region ({circle around (2)}) to the lengthfrom the radius point (6 mm, 7 mm, 8 mm, 9 mm) where the overlappinglayer number uniform region starts to the outermost point (22 mm) of theelectrode assembly, and the like for Examples 2-1 to 2-5, Examples 3-1to 3-4, Examples 4-1 to 4-3, and Examples 5-1 to Example 5-2.

TABLE 5 e. b. c. d. overlapping h. i. j. a. winding segment height layernumber f. g. ratio of ratio of ratio of core structure skip variableuniform segment number of segment height height radius radius regionregion region region overlapping c/(b − a) d/f e/f skip variable uniformRef. (mm) (mm) (mm) (mm) (mm) (mm) layers (%) (%) (%) region regionregion Example 2 22 4 2 7 16 16 20% 13% 44% 10%  6% 81% 2-1 Example 2 224 3 8 16 18 20% 19% 50% 10% 11% 77% 2-2 Example 2 22 4 4 9 16 21 20% 25%56% 10% 16% 72% 2-3 Example 2 22 4 5 10 16 24 20% 31% 63% 10% 20% 68%2-4 Example 2 22 4 6 11 16 26 20% 38% 69% 10% 25% 65% 2-5 Example 2 22 52 6 15 18 25% 13% 40% 13%  7% 77% 3-1 Example 2 22 5 3 7 15 21 25% 20%47% 13% 12% 72% 3-2 Example 2 22 5 4 8 15 24 25% 27% 53% 13% 16% 68% 3-3Example 2 22 5 5 9 15 26 25% 33% 60% 13% 22% 62% 3-4 Example 2 22 6 2 514 21 30% 14% 36% 16%  9% 72% 4-1 Example 2 22 6 3 6 14 24 30% 21% 43%16% 13% 68% 4-2 Example 2 22 6 4 7 14 26 30% 29% 50% 16% 19% 62% 4-3Example 2 22 7 2 4 13 24 35% 15% 31% 20%  9% 68% 5-1 Example 2 22 7 3 513 26 35% 23% 38% 20% 15% 62% 5-2

Seeing Example 2-5, Example 3-4, Example 4-3, and Example 5-2 of Table 5along with FIGS. 10 a and 10 d , the maximum height (h_(N)) of thesegment in the height variable region ({circle around (2)}) of thesegment is the same as 10 mm, but the minimum height (h₁) of the segmentincreases to 4 mm, 5 mm, 6 mm, and 7 mm by 1 mm, and the length of theheight variable region ({circle around (2)}) decreases to 6 mm, 5 mm, 4mm, 3 mm by 1 mm. In the four examples, the ratio (e/f) of theoverlapping layer number uniform region is the maximum in Example 2-5 as69% and the minimum in Example 5-2 as 38%, and the number of overlappinglayers of the overlapping layer number uniform region is the same in allexamples.

From the results shown in Table 5, when the maximum height (h_(N)) ofthe segment is the same and the minimum height (h₁) of the segmentdecreases, it may be understood that the width of the overlapping layernumber uniform region increases proportionally as the width of theheight variable region ({circle around (2)}) of the segment increases.The reason is that as the minimum length (h₁) of the segment is smaller,the radius point where the segment starts is closer to the core, so thatthe area where the segments are stacked is extended toward the core.

Seeing Table 5, it may be found that the number of overlapping layers ofthe segments is to 26, the ratio (d/f) of the height variable region({circle around (2)}) of the segment is 13% to 38%, and the ratio of theoverlapping layer number uniform region (e/f) is 31% to 69%. Inaddition, the ratio (c/(b-a)) of the segment skip region ({circle around(1)}) to the radius (b-a) of the electrode assembly excluding the coreis 20% to 35%. In addition, the ratio of the length of the electrodearea corresponding to the segment skip region ({circle around (1)}) tothe total length of the electrode is 10% to 20%, the ratio of the lengthof the electrode area corresponding to the height variable region({circle around (2)}) to the total length of the electrode is 6% to 25%,and the ratio of the length of the electrode area corresponding to theheight uniform region ({circle around (3)}) to the total length of theelectrode is 62% to 81%.

In the cylindrical battery form factors of 1865 and 2170, the radius ofthe electrode assembly is approximately 9 mm to 10 mm. Therefore, it isimpossible that the radial length of the segment region (f) is securedat the level of 13 mm to 16 mm as in the examples, and it is impossiblethat the length of the segment skip region (c, {circle around (1)}) issecured in the level of 4 mm to 7 mm while the length of the overlappinglayer number uniform region (e) in which the number of overlappinglayers of the segments is 10 or more is secured in the level of 5 mm to11 mm. This is because, in the conventional cylindrical battery, whenthe radius of the core is designed to be 2 mm, which is the same as inthe examples, the radial region in which the segments can be disposed issubstantially only 7 mm to 8 mm. In addition, in the conventionalcylindrical battery, the length of the electrode in the windingdirection is in the level of 600 mm to 980 mm. Such a short electrodelength is only about 15% to 24% of the electrode length (the positiveelectrode of 3948 mm, the negative electrode of 4045 mm) in theexamples. Accordingly, the numerical ranges for the parameters h, i andj cannot be easily derived from the design specifications of theconventional cylindrical battery.

Next, it will be explained through specific examples how the number ofoverlapping layers of the segments is changed according to the diameterof the core C of the electrode assembly along the radial direction ofthe bending surface region F when the minimum height (h₁) and themaximum height (h_(N)) of the segment are the same in the heightvariable region ({circle around (2)}) of the segment.

The electrode assemblies of Examples 6-1 to 6-6 have a radius of 22 mm,and the core C has a radius of 4 mm. In the height variable region({circle around (2)}) of the segment 61, the minimum height (h₁) of thesegment is the same as 3 mm, and the maximum height (h_(N)) of thesegment is changed from 5 mm to 10 mm by 1 mm. Therefore, in theelectrode assemblies of Examples 6-1 to 6-6, the width of the heightvariable region ({circle around (2)}) of the segment is 2 mm, 3 mm, 4mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment skip region({circle around (1)}) is a radial region having a radius from 4 mm to 7mm.

The electrode assemblies of Examples 7-1 to 7-6 have a radius of 22 mm,and the core C has a radius of 2 mm. In the height variable region({circle around (2)}) of the segment 61, the minimum height (h₁) of thesegment is the same as 3 mm, and the maximum height (h_(N)) of thesegment is changed from 5 mm to 10 mm by 1 mm. Therefore, in theelectrode assemblies of Examples 7-1 to 7-6, the width of the heightvariable region ({circle around (2)}) of the segment is 2 mm, 3 mm, 4mm, 5 mm, 6 mm, and 7 mm, respectively, and the segment skip region({circle around (1)}) is a radial region having a radius from 2 mm to 5mm.

FIG. 10 e are graphs showing the results of counting the number ofoverlapping layers of the segments measured along the radial directionin the bending surface region F of the positive electrode formed on theupper portion of the electrode assembly for Examples 6-1 to 6-6 andExamples 7-1 to 7-6. Substantially the same results are shown in thebending surface region of the negative electrode.

In FIG. 10 e , Graph (a) shows the results of counting the number ofoverlapping layers of segments measured along the radial direction inthe bending surface region F for Examples 6-1 to 6-6, and Graph (b)shows the results for Examples 7-1 to 7-6.

Referring to FIG. 10 e , the overlapping layer number uniform region b1of the segment appears in common in all examples. The overlapping layernumber uniform region b1 is a radial region of a flat region in thegraph. The radial length of the overlapping layer number uniform regionb1 increases as the maximum height (h_(N)) of the segment decreases whenthe minimum height (h₁) of the segment is the same. Meanwhile, in theoverlapping layer number uniform region b1, the number of overlappinglayers of the segments increases as the maximum height (h_(N)) of thesegment increases. In the examples, the overlapping layer numberdecreasing region b2 appears adjacent to the overlapping layer numberuniform region b1.

In the examples, the number of overlapping layers of the segments in theoverlapping layer number uniform region b1 is 10 or more for allexamples. Preferably, a region in which the number of overlapping layersof segments is 10 or more may be set as a welding target region.

In the examples, the overlapping layer number uniform region b1 startsfrom a radius point where the height variable region ({circle around(2)}) of the segment starts. In Examples 6-1 to 6-6, the radius at whichthe segment height variable region ({circle around (2)}) starts is 7 mm,and in Examples 7-1 to 7-6, the radius at which the segment heightvariable region ({circle around (2)}) starts is 5 mm.

Table 6 below shows the results of calculating various parametersincluding a ratio (e/f) of the length of the overlapping layer numberuniform region to the length from the radius point (7 mm, 5 mm) wherethe overlapping layer number uniform region starts to the outermostpoint (22 mm) of the electrode assembly, a ratio (d/f) of the length ofthe height variable region ({circle around (2)}) to the length from theradius point (7 mm, 5 mm) where the overlapping layer number uniformregion starts to the outermost point (22 mm) of the electrode assembly,for Examples 6-1 to 6-6 and Examples 7-1 to 7-6, and the like.

TABLE 6 e. b. c. d. overlapping h. i. j. a. winding segment height layernumber f. g. ratio of ratio of ratio of core structure skip variableuniform segment number of segment height height radius radius regionregion region region overlapping c/(b − a) d/f e/f skip variable uniformRef. (mm) (mm) (mm) (mm) (mm) (mm) layers (%) (%) (%) region regionregion Example 4 22 3 2 11 15 13 17% 13% 73% 6%  7% 83% 6-1 Example 4 223 3 10 15 16 17% 20% 67% 6% 11% 80% 6-2 Example 4 22 3 4 9 15 18 17% 27%60% 6% 15% 75% 6-3 Example 4 22 3 5 8 15 21 17% 33% 53% 6% 21% 69% 6-4Example 4 22 3 6 7 15 24 17% 40% 47% 6% 25% 65% 6-5 Example 4 22 3 7 615 26 17% 47% 40% 6% 32% 59% 6-6 Example 2 22 3 2 13 17 13 15% 12% 76%6%  7% 83% 7-1 Example 2 22 3 3 12 17 16 15% 18% 71% 6% 11% 80% 7-2Example 2 22 3 4 11 17 18 15% 24% 65% 6% 15% 75% 7-3 Example 2 22 3 5 1017 21 15% 29% 59% 6% 21% 69% 7-4 Example 2 22 3 6 9 17 24 15% 35% 53% 6%25% 65% 7-5 Example 2 22 3 7 8 17 26 15% 41% 47% 6% 32% 59% 7-6

Seeing Examples 6-6 and 7-6 in Table 6 along with FIG. 10 a , theminimum height (h₁) and the maximum height (h_(N)) of the segment in theheight variable region ({circle around (2)}) of the segment are the sameas 3 mm and 10 mm, respectively. However, in Example 6-6, the radius ofthe core is larger by 2 mm compared to that of Example 7-6. Therefore,in Example 6-6, the overlapping layer number uniform region (e) and thesegment region (f) are smaller by 2 mm compared to those of Example 7-6,and the number of overlapping layers of the segments in the overlappinglayer number uniform region is the same. These results are derived fromthe difference in the radius of the core. From the results shown inTable 6, it may be understood that, when the width of the heightvariable region ({circle around (2)}) of the segment is the same, as theradius (a) of the core is smaller, the ratio (d/f) of the heightvariable region ({circle around (2)}) decreases, whereas the ratio (e/f)of the overlapping layer number uniform region increases.

Seeing Table 6, it may be found that the number of overlapping layers ofthe segments is to 26, the ratio (d/f) of the height variable region({circle around (2)}) is 12% to 47%, and the ratio (e/f) of the lengthof the overlapping layer number uniform region is 40% to 76%. Inaddition, the ratio (c/(b-a)) of the segment skip region ({circle around(1)}) to the radius (b-a) of the electrode assembly excluding the coreis 15% to 17%. In addition, the ratio of the length of the electrodearea corresponding to the segment skip region ({circle around (1)}) tothe total length of the electrode is 6%, the ratio of the length of theelectrode area corresponding to the height variable region ({circlearound (2)}) to the total length of the electrode is 7% to 32%, and theratio of the length of the electrode area corresponding to the heightuniform region ({circle around (3)}) to the total length of theelectrode is 59% to 83%.

For the cylindrical batteries with form factors of 1865 and 2170, theradius of the electrode assembly is approximately 9 mm to 10 mm.Therefore, it is impossible that the radial length of the segment region(f) is secured in the level of 15 mm to 17 mm, and the length of thesegment skip region ({circle around (1)}) is secured in the level ofabout 3 mm, and simultaneously the length of the overlapping layernumber uniform region (e) in which the number of overlapping layers ofthe segments is 10 or more is secured in the level of 6 mm to 13 mm asin the examples. This is because, in the conventional cylindricalbattery, when the radius of the core is designed to be 2 mm to 4 mm,which is the same as in the examples, the radial region in whichsegments can be disposed is substantially only 5 mm to 8 mm. Inaddition, in the conventional cylindrical battery, the length of theelectrode in the winding direction is in the level of 600 mm to 980 mm.Such a short electrode length is only about 15% to 24% of the electrodelength (the positive electrode of 3948 mm, the negative electrode of4045 mm) in the examples. Accordingly, the numerical ranges for theparameters h, i and j may not be easily derived from the designspecifications of the conventional cylindrical battery.

Comprehensively considering the data in Tables 4 to 6, the number ofoverlapping layers of the segments in the overlapping layer numberuniform region of the segment may be 11 to 26. Also, the ratio (d/f) ofthe height variable region ({circle around (2)}) of the segment may be6% to 47%. In addition, the ratio (e/f) of the overlapping layer numberuniform region may be 31% to 82%. In addition, the ratio (c/(b-a)) ofthe length of the segment skip region ({circle around (1)}) to theradius of the electrode assembly excluding the core may be 15% to 35%.In addition, the ratio of the length of the electrode area correspondingto the segment skip region ({circle around (1)}) to the total length (inthe winding direction length) of the electrode may be 6% to 20%. Inaddition, the ratio of the length of the electrode area corresponding tothe height variable region ({circle around (2)}) of the segment to thetotal length of the electrode may be 3% to 32%. In addition, the ratioof the length of the electrode area corresponding to the height uniformregion ({circle around (3)}) of the segment to the total length of theelectrode may be 59% to 87%.

Meanwhile, the parameters described through Tables 4 to 6 may be variedaccording to design factors including the radius (a) of the core; theradius (b) of the electrode assembly; the minimum height (h₁) and themaximum height (h_(N)) in the height variable region ({circle around(2)}) of the segment; the change amount (Δh) in height of the segmentper 1 mm increase in radius; the thickness of the positive electrode,the negative electrode, and the separator; and the like.

Therefore, in the overlapping layer number uniform region of thesegment, the number of overlapping layers of the segments may beexpanded to 10 to 35. The ratio (d/f) of the height variable region({circle around (2)}) of the segment may be expanded to 1% to 50%. Inaddition, the ratio (e/f) of the overlapping layer number uniform regionmay be expanded to 30% to 85%. In addition, the ratio (c/(b−a)) of thelength of the segment skip region ({circle around (1)}) to the radius ofthe electrode assembly excluding the core may be expanded to 10% to 40%.In addition, the ratio of the length of the electrode area correspondingto the segment skip region ({circle around (1)}) to the total length (inthe winding direction length) of the electrode may be expanded to 1% to30%. In addition, the ratio of the length of the electrode areacorresponding to the height variable region ({circle around (2)}) of thesegment to the total length of the electrode may be expanded to 1% to40%. In addition, the ratio of the length of the electrode areacorresponding to the height uniform region ({circle around (3)}) of thesegment to the total length of the electrode may be expanded to 50% to90%. In the above examples, the height index ‘N’ in the maximum height(h_(N)) of the segment in the height variable region ({circle around(2)}) and the height uniform region ({circle around (3)}) is in therange of 2 to 8. For example, referring to Table 4, the height index ‘N’for examples 1-1 and 1-7 is 2 and 8, respectively. However, the heightindex ‘N’ may vary in accordance with the height change amount (Δh) ofthe segment in a radial direction of the electrode assembly. When theradial length of the height variable region ({circle around (2)}) isfixed, as the height change amount (Δh) of the segment decreases, theheight index ‘N’ correspondingly increases and vice versa. Preferably,the height index ‘N’ may be expanded to the range of 2 to 20 and,optionally, further to the range of 2 to 30.

In the bending surface region F formed at the top and bottom of theelectrode assembly, the overlapping layer number uniform region may beused as a welding target region of the current collector.

Preferably, the welding region of the current collector overlaps atleast 50% with the overlapping layer number uniform region in the radialdirection of the electrode assembly. Here, the overlapping ratio may behigher.

Preferably, the remaining region of the welding region of the currentcollector that does not overlap with the overlapping layer numberuniform region may overlap with the overlapping layer number decreasingregion adjacent to the overlapping layer number uniform region in theradial direction.

The remaining region of the welding region of the current collector thatdoes not overlap with the overlapping layer number uniform region mayoverlap with a region of the overlapping layer number decreasing regionin which the number of overlapping layers of segments is 10 or more.

If the current collector is welded to the region where the number ofoverlapping layers of the segments is 10 or more, it is preferable interms of welding strength and in terms of preventing damage to theseparator or the active material layer during welding. In particular, itis useful when welding the current collector using a high-power laserwith high penetration characteristics.

If the overlapping layer number uniform region in which 10 or moresegments are stacked is welded to the current collector with a laser,even if the laser output is increased to improve the welding quality,the overlapping layer number uniform region absorbs most of the laserenergy to form welding beads, so it is possible to prevent the separatorand the active material layer under the bending surface region F frombeing damaged by the laser.

In addition, in the area irradiated with laser, the number ofoverlapping layers of segments is 10 or more, so welding beads areformed with sufficient volume and thickness. Accordingly, the weldingstrength may be sufficiently secured and the resistance of the weldinginterface may be lowered to a level suitable for rapid charging.

When welding the current collector, the laser output may be determinedby the desired welding strength between the bending surface region F andthe current collector. The welding strength increases proportionallywith the number of overlapping layers of segments. This is because asthe number of overlapping layers increases, the volume of welding beadsformed by the laser increases. The welding beads are formed when thematerial of the current collector and the material of the segment aremelted together. Therefore, if the volume of the welding beads is large,the current collector and the bending surface region are coupledstronger and the contact resistance of the welding interface is lowered.

The welding strength may be 2 kgf/cm² or more, more particularly 4kgf/cm² or more. The maximum welding strength may be dependent on apower of a laser welding equipment. As one example, the welding strengthmay be set to 8 kgf/cm² or less, more particularly 6 kgf/cm² or less,but the present invention is not limited thereto.

If the welding strength satisfies the above numerical range, thephysical properties of the welding interface do not deteriorate even ifsevere vibration is applied to the electrode assembly along the windingaxis direction and/or the radial direction, and the resistance of thewelding interface may also be reduced due to the sufficient volume ofthe welding beads.

The laser power to satisfy the welding strength condition variesdepending on the laser equipment, and it may be appropriately adjustedin the range of 250 W to 320 W or 40% to 100% of the maximum laser powerspecification provided by the corresponding equipment.

The welding strength may be defined as a tensile force per unit area(kgf/cm²) of the current collector when the current collector starts toseparate from the bending surface region F. Specifically, after thecurrent collector is completely welded, a tensile force may be appliedto the current collector, but the magnitude of the tensile force may begradually increased. If the tensile force exceeds a threshold, thesegment begins to separate from the welding interface. At this time, thevalue obtained by dividing the tensile force applied to the currentcollector by the area of the current collector corresponds to thewelding strength.

In the bending surface region F, segments are stacked into multiplelayers, and according to the above embodiments, the number ofoverlapping layers of the segments may be increased from 10 sheets atminimum to 35 sheets at maximum.

The thickness of the positive electrode current collector (foil)constituting an uncoated portion 43 may be in the range of 10 μm to 25μm, and the thickness of the negative electrode current collector (foil)constituting an uncoated portion 43 may be in the range of 5 μm to 20μm. Therefore, the bending surface region F of the positive electrodemay include a region where the total overlapping thickness of thesegments is 100 μm to 875 um. In addition, the bending surface region Fof the negative electrode may include a region where the totaloverlapping thickness of the segments is 50 μm to 700 μm.

FIG. 10 f is a top plan view showing an electrode assembly in which theoverlapping layer number uniform region b1 and the overlapping layernumber decreasing region b2 are depicted in the bending surface region Fof the segments 61, 61′ according to an embodiment of the presentdisclosure.

Referring to FIG. 10 f , the area between two circles indicated by thicksolid lines corresponds to the bending surface region F of the segment,and the area between two circles indicated by dashed-dotted linescorresponds to the overlapping layer number uniform region b1 in whichthe number of overlapping layers of the segments is 10 or more, and theouter region of the overlapping layer number uniform region b1corresponds to the overlapping layer number decreasing region b2.

In one example, if the current collector (P_(c)) is welded to thebending surface region F, a welding pattern (W_(p)) is formed on thesurface of the current collector (P_(c)). The welding pattern (W_(p))may be a line pattern or a dot array pattern. The welding pattern(W_(p)) corresponds to the welding region, and may overlap with theoverlapping layer number uniform region b1 of the segment by 50% or morealong the radial direction. Accordingly, a part of the welding pattern(W_(p)) may be included in the overlapping layer number uniform regionb1, and the remainder of the welding pattern (W_(p)) may be included inthe overlapping layer number decreasing region b1 outside theoverlapping layer number uniform region b1. Of course, the entirewelding pattern (W_(p)) may overlap with the overlapping layer numberuniform region b1 in order to maximize a welding strength and lower aresistance in the welding region.

The area of the bending surface region F may be defined as the sum ofthe area of the overlapping layer number uniform region b1 of thesegment and the area of the overlapping layer number decreasing regionb2. Since the ratio (e/f) of the overlapping layer number uniform regionb1 is 30% to 85%, preferably 31% to 82%, the ratio of the area of theoverlapping layer number uniform region b1 to the area of the bendingsurface region F may be 9% (30²/100²) to 72% (85²/100²), preferably 10%(31²/100²) to 67% (82²/100²).

Preferably, the edge of the portion where the current collector (Pc)contacts the bending surface region F may cover the end of the segments61, 61′ bent toward the core C in the last winding turn of the heightuniform region ({circle around (3)}). In this case, since a weldingpattern (W_(p)) is formed in a state where the segments 61, 61′ arepressed by the current collector (P_(c)), the current collector (P_(c))and the bending surface region F are strongly coupled. As a result, thesegments 61, 61′ stacked in the winding axis direction are closelyadhered to each other, thereby lowering the resistance at the weldinginterface and preventing the segments 61, 61′ from lifting.

Meanwhile, the bending direction of the segment may be opposite to thatdescribed above. That is, the segment may be bent from the core towardthe outer circumference. In this case, the pattern in which the heightof the segment is changed along the winding direction (X-axis direction)may be opposite to that of the former embodiments (modified examples).For example, the height of the segment may be lowered stepwise from thecore toward the outer circumference. Also, the structure applied to thefirst part B1 and the structure applied to the second part B3 may beswitched with each other. Preferably, the height change pattern of thesegment may be designed such that the height of the segment is graduallydecreased from the core side to the outer circumference side, but theend of the segment is not exposed out of the outer circumference of theelectrode assembly when the segment closest to the outer circumferenceof the electrode assembly is bent toward the outer circumference.

The electrode structure of the above embodiments (modifications) may beapplied to at least one of the first electrode and the second electrodehaving different polarities included in the jelly-roll type electrodeassembly or other type of electrode assembly known in the art. Inaddition, when the electrode structure of the above embodiments(modifications) is applied to any one of the first electrode and thesecond electrode, the conventional electrode structure may be applied tothe other one. In addition, the electrode structures applied to thefirst electrode and the second electrode may not be identical but bedifferent from each other.

For example, when the first electrode and the second electrode are apositive electrode and a negative electrode, respectively, any one ofthe above embodiments (modifications) may be applied to the firstelectrode and the conventional electrode structure (see FIG. 1 ) may beapplied to the second electrode.

As another example, when the first electrode and the second electrodeare a positive electrode and a negative electrode, respectively, any oneof the above embodiments (modifications) may be selectively applied tothe first electrode and any one of the above embodiments (modifications)may be selectively applied to the second electrode.

In the present disclosure, a positive electrode active material coatedon the positive electrode and a negative electrode active materialcoated on the negative electrode may employ any active material known inthe art without limitation.

In one example, the positive electrode active material may include analkali metal compound expressed by a general formulaA[A_(x)M_(y)]O_(2+z) (A includes at least one element among Li, Na andK; M includes at least one element selected from is Ni, Co, Mn, Ca, Mg,Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≥0,1≤x+y≤2, −0.1≤z≤2; and the stoichiometric modulus x, y and z areselected so that the compound maintains electrical neutrality).

In another example, the positive electrode active material may be analkali metal compound xLiM¹O₂-(1-x)Li₂M²O₃ disclosed in U.S. Pat. Nos.6,677,082, 6,680,143, et al., wherein M¹ includes at least one elementhaving an average oxidation state 3; M² includes at least one elementhaving an average oxidation state 4; and 0≤x≤1).

In still another example, the positive electrode active material may belithium metal phosphate expressed by a general formula Li_(a)M¹_(x)Fe_(1-x)M² _(y)P_(1-y)M³ _(z)O_(4-z) (M¹ includes at least oneelement selected from the Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mgand Al; M² includes at least one element selected from Ti, Si, Mn, Co,Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V and S; M³ includesa halogen element optionally including F; 0<a≤2, 0≤x≤1, 0≤y<1, 0≤z<1;the stoichiometric coefficient a, x, y and z are selected so that thecompound maintains electrical neutrality), or Li₃M₂(PO₄)₃ (M includes atleast one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al,Mg and Al).

Preferably, the positive electrode active material may include primaryparticles and/or secondary particles in which the primary particles areaggregated.

In one example, the negative electrode active material may employ carbonmaterial, lithium metal or lithium metal compound, silicon or siliconcompound, tin or tin compound, or the like. Metal oxides such as TiO₂and SnO₂ with a potential of less than 2V may also be used as thenegative electrode active material. As the carbon material, bothlow-crystalline carbon, high-crystalline carbon or the like may be used.

The separator may employ a porous polymer film, for example, a porouspolymer film made of a polyolefin-based polymer such as ethylenehomopolymer, propylene homopolymer, ethylene/butene copolymer,ethylene/hexene copolymer, ethylene/methacrylate copolymer, or the like,or laminates thereof. As another example, the separator may employ acommon porous nonwoven fabric, for example, a nonwoven fabric made ofhigh melting point glass fiber, polyethylene terephthalate fiber, or thelike.

A coating layer of inorganic particles may be included in at least onesurface of the separator. It is also possible that the separator itselfis made of a coating layer of inorganic particles. Particles in thecoating layer may be coupled with a binder so that an interstitialvolume exists between adjacent particles.

The inorganic particles may be made of an inorganic material having adielectric constant of 5 or more. As a non-limiting example, theinorganic particles may include at least one material selected from thegroup consisting of Pb(Zr,Ti)O₃ (PZT), Pb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃(PLZT), PB(Mg₃Nb_(2/3))O₃—PbTiO₃ (PMN-PT), BaTiO₃, hafnia (HfO₂),SrTiO₃, TiO₂, Al₂O₃, ZrO₂, SnO₂, CeO₂, MgO, CaO, ZnO and Y₂O₃.

Hereinafter, the structure of the electrode assembly according to anembodiment of the present disclosure will be described in detail.

FIG. 11 is a sectional view showing a jelly-roll type electrode assembly80 in which the electrode 40 of the first embodiment is applied to thefirst electrode (the positive electrode) and the second electrode (thenegative electrode), taken along the Y-axis direction (winding axisdirection).

The electrode assembly 80 may be manufactured by the winding methoddescribed with reference to FIG. 2 . For convenience of description, theprotruding structures of the first uncoated portion 43 a and the seconduncoated portion 43 b extending out of the separator are illustrated indetail, and the winding structures of the first electrode, the secondelectrode, and the separator are not depicted. The first uncoatedportion 43 a protruding upward extends from the first electrode, and thesecond uncoated portion 43 b protruding downward extends from the secondelectrode.

The patterns in which the heights of the first and second uncoatedportions 43 a, 43 b change are schematically illustrated. That is, theheight of the uncoated portion may vary irregularly depending on theposition at which the cross-section is cut. For example, at across-section where the sides of the trapezoidal segments 61, 61′ or thecut grooves 63 are cut, the height of the uncoated portion in the crosssection is lower than the height H of the segments 61, 61′. Accordingly,it should be understood that the heights of the uncoated portionsdepicted in the drawings showing the cross-section of the electrodeassembly correspond to the average of the heights (H in FIGS. 7 b and 8b ) of the uncoated portion included in each winding turn.

Referring to FIG. 11 , the first uncoated portion 43 a includes a firstpart B1 adjacent to the core of the electrode assembly 80, a second partB3 adjacent to the outer circumference of the electrode assembly 80, anda third part B2 interposed between the first part B1 and the second partB3.

The height (length in the Y-axis direction) of the second part B3 isrelatively smaller than the height of the third part B2. Accordingly, itis possible to prevent that an internal short circuit occurs since thebeading portion and the second part B3 contact each other while thebeading portion of the battery housing is being pressed near the secondpart B3.

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In one modification, the second uncoated portion43 b may have a conventional electrode structure or an electrodestructure of other embodiments (modifications).

The ends 81 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent in the radial direction of the electrodeassembly 80, for example from the outer circumference toward the core.At this time, the second part B3 may not be substantially bent.

FIG. 12 is a sectional view showing a jelly-roll type electrode assembly90 in which the electrode 45 of the second embodiment is applied to thefirst electrode (the positive electrode) and the second electrode (thenegative electrode), taken along the Y-axis direction (winding axisdirection).

Referring to FIG. 12 , the first uncoated portion 43 a includes a firstpart B1 adjacent to the core of the electrode assembly 90, a second partB3 adjacent to the outer circumference of the electrode assembly 90, anda third part B2 interposed between the first part B1 and the second partB3.

The height of the second part B3 is relatively smaller than the heightof the third part B2 and decreases gradually or stepwise from the coreto the outer circumference. Accordingly, it is possible to prevent thatan internal short circuit occurs since the beading portion and thesecond part B3 contact each other while the beading portion of thebattery housing is being pressed near the second part B3.

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In one modification, the second uncoated portion43 b may have a conventional electrode structure or an electrodestructure of other embodiments (modifications).

The ends 91 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent in the radial direction of the electrodeassembly 90, for example from the outer circumference to the core. Atthis time, the outermost portion 92 of the second part B3 may not besubstantially bent.

FIG. 13 is a sectional view showing a jelly-roll type electrode assembly100 in which any one of the electrodes 50, 60, 70 of the third to fifthembodiments (modifications thereof) are applied to the first electrode(the positive electrode) and the second electrode (the negativeelectrode), taken along the Y-axis direction (winding axis direction).

Referring to FIG. 13 , the first uncoated portion 43 a includes a firstpart B1 adjacent to the core of the electrode assembly 100, a secondpart B3 adjacent to the outer circumference of the electrode assembly100, and a third part B2 interposed between the first part B1 and thesecond part B3.

The height of the first part B1 is relatively smaller than the height ofthe third part B2. In addition, the bending length of the uncoatedportion 43 a located at the innermost side of the third part B2 is equalto or smaller than the radial length (R) of the first part B1. Thebending length (H) corresponds to the distance from the bending point ofthe uncoated portion 43 a to the top of the uncoated portion 43 a. In amodified example, the bending length (H) may be smaller than the sum ofthe radial length (R) of the first part B1 and 10% of the radius of thecore 102.

Therefore, even if the third part B2 is bent, the core 102 of theelectrode assembly 100 is open to the outside by 90% or more of thediameter of the core 102. The core 102 is a cavity at the center of theelectrode assembly 100. If the core 102 is not blocked, there is nodifficulty in the electrolyte injection process, and the electrolyteinjection efficiency is improved. In addition, by inserting a weldingjig through the core 102, the welding process may be easily performedbetween the current collector of the negative electrode (or, thepositive electrode) and the battery housing (or, the terminal).

The height of the second part B3 is relatively smaller than the heightof the third part B2. Accordingly, while the beading portion of thebattery housing is being pressed near the second part B3, it is possibleto prevent the beading portion and the second part B3 from coming intocontact with each other to cause an internal short circuit.

In one modification, the height of the second part B3 may be decreasedgradually or stepwise, unlike that shown in FIG. 13 . Also, in FIG. 13 ,although the height of the third part B2 is partially the same in acircumferential direction, the height of the third part B2 may increasegradually or stepwise from the boundary between the first part B1 andthe third part B2 to the boundary between the third part B2 and thesecond part B3. When the third part B2 is divided into a plurality ofsegments, a region in which the height of the uncoated portion 43 achanges corresponds to the height variable region ({circle around (2)})in FIG. 10 a ) of the segment.

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In one modification, the second uncoated portion43 b may have a conventional electrode structure or an electrodestructure of other embodiments (modifications).

The ends 101 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent in the radial direction of the electrodeassembly 100, for example from the outer circumference to the core. Atthis time, the first part B1 and the second part B3 are notsubstantially bent.

When the third part B2 includes a plurality of segments, the bendingstress may be relieved to prevent the uncoated portion 43 a near thebending point from being torn or abnormally deformed. In addition, whenthe width and/or height and/or separation pitch of the segment isadjusted according to the numerical range of the above embodiment, thesegments are bent toward the core and overlap in multiple layers tosufficiently secure the welding strength, and an empty hole (gap) is notformed in the bent surface region.

FIG. 14 is a sectional view showing an electrode assembly 110 accordingto still another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

Referring to FIG. 14 , the electrode assembly 110 is substantially thesame as the electrode assembly 100 of FIG. 13 , except that the heightof the second part B3 is substantially the same as the height of theoutermost side of the third part B2.

The second part B3 may include a plurality of segments. Theconfiguration of the plurality of segments is substantially the same asdescribed in the fourth and fifth embodiments (modifications) related toelectrodes.

In the electrode assembly 110, the height of the first part B1 isrelatively smaller than the height of the third part B2. Also, thebending length (H) of the uncoated portion located at the innermost sideof the third part B2 is equal to or smaller than the radial length (R)of the first part B1. Preferably, the first part B1 may be the segmentskip region having no segment (0 in FIG. 10 a ). In a modified example,the bending length (H) may be smaller than the sum of the radial length(R) of the first part B1 and 10% of the radius of the core 102.

Therefore, even if the third part B2 is bent, the core 112 of theelectrode assembly 110 is opened to the outside by at least 90% or moreof the diameter of the core 112. If the core 112 is not blocked, thereis no difficulty in the electrolyte injection process and theelectrolyte injection efficiency is improved. In addition, by insertinga welding jig through the core 112, the welding process may be easilyperformed between the current collector of the negative electrode (or,the positive electrode) and the battery housing (or, the terminal).

In one modification, the structure in which the height of the third partB2 increases gradually or stepwise from the core toward the outercircumference may be extended to the second part B3. In this case, theheight of the uncoated portion 43 a may be increased gradually orstepwise from the boundary between the first part B1 and the third partB2 to the outermost surface of the electrode assembly 110.

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In one modification, the second uncoated portion43 b may have a conventional electrode structure or an electrodestructure of other embodiments (modifications).

The ends 111 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent in the radial direction of the electrodeassembly 110, for example from the outer circumference toward the core.At this time, the first part B1 is not substantially bent.

When the third part B2 and the second part B3 include a plurality ofsegments, the bending stress may be relieved to prevent the uncoatedportions 43 a, 43 b near the bending point from being torn or abnormallydeformed. In addition, when the width and/or height and/or separationpitch of the segment is adjusted according to the numerical range of theabove embodiment, the segments are bent toward the core and overlap inmultiple layers to sufficiently secure the welding strength, and anempty hole (gap) is not formed in the bent surface region.

FIG. 15 is a sectional view showing an electrode assembly 120 accordingto still another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

Referring to FIG. 15 , the electrode assembly 120 is substantially thesame as the electrode assembly 100 of FIG. 13 , except that the heightof the third part B2 has a pattern increasing and then decreasinggradually or stepwise. The radial region in which the height of thethird part B2 changes may be regarded as the height variable region({circle around (2)} in FIG. 10 a ) of the segment. Even in this case,the height variable region of the segment may be designed so that theoverlapping layer number uniform region in which the number ofoverlapping layers of segments is 10 or more appears in the numericalrange described above in the bending surface region F formed by bendingthe third part B2.

This change in height of the third part B2 may be implemented by usingthe step pattern (see FIG. 6 ) or adjusting the height of segments (seeFIG. 7 a or 8 a) included in the third part B2.

In the electrode assembly 120, the height of the first part B1 isrelatively smaller than the height of the third part B2. Also, thebending length (H) of the uncoated portion located at the innermost sideof the third part B2 is equal to or smaller than the radial length (R)of the first part B1. The region corresponding to the first part B1corresponds to the segment skip region having no segment ({circle around(1)} in FIG. 10 a ). In a modified example, the bending length (H) maybe smaller than the sum of the radial length (R) of the first part B1and 10% of the radius of the core 102.

Therefore, even if the third part B2 is bent toward the core, the core122 of the electrode assembly 120 is opened to the outside by at least90% or more of its diameter. If the core 122 is not blocked, there is nodifficulty in the electrolyte injection process and the electrolyteinjection efficiency is improved. In addition, by inserting a weldingjig through the core 122, the welding process may be easily performedbetween the current collector of the negative electrode (or, thepositive electrode) and the battery housing (or, the terminal).

Also, the height of the second part B3 is relatively smaller than theheight of the third part B2, and preferably no segment may be formed inthe second part B3. Accordingly, it is possible to prevent that aninternal short circuit occurs since the beading portion and the secondpart B3 contact each other while the beading portion of the batteryhousing is being pressed near the second part B3. In one modification,the height of the second part B3 may decrease gradually or stepwisetoward the outer circumference.

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In a modification, the second uncoated portion 43b may have a conventional electrode structure or an electrode structureof other embodiments (modifications).

The ends 121 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent from the outer circumference of the electrodeassembly 120 to the core. At this time, the first part B1 and the secondpart B3 are not substantially bent.

When the third part B2 includes a plurality of segments, the bendingstress may be relieved to prevent the uncoated portions 43 a, 43 b frombeing torn or abnormally deformed. In addition, when the width and/orheight and/or separation pitch of the segment is adjusted according tothe numerical range of the above embodiment, the segments are benttoward the core and overlap in multiple layers to sufficiently securethe welding strength, and an empty hole (gap) is not formed in the bentsurface region.

FIG. 16 is a sectional view showing an electrode assembly 130 accordingto still another embodiment of the present disclosure, taken along theY-axis direction (winding axis direction).

Referring to FIG. 16 , the electrode assembly 130 is substantially thesame as the electrode assembly 120 of FIG. 15 , except that the heightof the second part B3 has a pattern that decreases gradually or stepwisefrom the boundary point of the second part B3 and the third part B2toward the outermost surface of the electrode assembly 130.

This change in the height of the second part B3 may be implemented byextending the step pattern (see FIG. 6 ) included in the third part B2to the second part B3 while simultaneously decreasing the height of thepattern toward the outer circumference gradually or stepwise. Inaddition, in another modification, the change in height of the secondpart B3 may be implemented by extending the segment structure of thethird part B2 to the second part B3 while simultaneously decreasing theheight of the segments gradually or stepwise toward the outercircumference.

In the electrode assembly 130, the height of the first part B1 isrelatively smaller than the height of the third part B2. Also, in thethird part B2, the bending length (H) of the innermost uncoated portionis equal to or smaller than the radial length (R) of the first part B1.The first part B1 corresponds to the segment skip region having nosegment ({circle around (1)} in FIG. 10 a ). In a modified example, thebending length (H) may be smaller than the sum of the radial length (R)of the first part B1 and 10% of the radius of the core 102.

Accordingly, even if the third part B2 is bent toward the core, the core132 of the electrode assembly 130 is opened to the outside by at least90% or more of its diameter. If the core 132 is not blocked, there is nodifficulty in the electrolyte injection process and the electrolyteinjection efficiency is improved. In addition, by inserting a weldingjig through the core 132, the welding process may be easily performedbetween the current collector of the negative electrode (or, thepositive electrode) and the battery housing (or, the terminal).

The second uncoated portion 43 b has the same structure as the firstuncoated portion 43 a. In one modification, the second uncoated portion43 b may have a conventional electrode structure or an electrodestructure of other embodiments (modifications).

The ends 131 of the first uncoated portion 43 a and the second uncoatedportion 43 b may be bent from the outer circumference of the electrodeassembly 130 to the core. At this time, the first part B1 is notsubstantially bent.

When the third part B2 and the second part B3 include a plurality ofsegments, the bending stress may be relieved to prevent the uncoatedportions 43 a, 43 b near the bending point from being torn or abnormallydeformed. In addition, when the width and/or height and/or separationpitch of the segment is adjusted according to the numerical range of theabove-described embodiment, the segments are bent toward the core andoverlap in multiple layers to sufficiently secure the welding strength,and an empty hole (gap) is not formed in the bent surface region.

Meanwhile, in the former embodiments (modified examples), the ends ofthe first uncoated portion 43 a and the second uncoated portion 43 b maybe bent from the core toward the outer circumference. In this case, itis preferable that the second part B3 is designed as the segment skipregion having no segment (0 in FIG. 10 a ) and is not bent toward theouter circumference. In addition, the width of the second part B3 in theradial direction may be equal to or greater than the length at which theoutermost uncoated portion (or segment) of the third part B2 is bent.Only then, when the outermost uncoated portion (or segment) of the thirdpart B2 is bent toward the outer circumference, the end of the bentportion does not protrude toward the inner surface of the batteryhousing beyond the outer circumference of the electrode assembly. Also,the change pattern of the segment structure may be opposite to theformer embodiments (modified examples). For example, the height of thesegment may be increased stepwise or gradually from the core toward theouter circumference. That is, by arranging the segment skip region({circle around (1)} of FIG. 10 a ), the height variable region ({circlearound (2)} of FIG. 10 a ) of the segment, and the height uniform region({circle around (3)} of FIG. 10 a ) of the segment from the outercircumference of the electrode assembly to the core in order, theoverlapping layer number uniform region in which the number ofoverlapping layers of segments is 10 or more may appear in a desirednumerical range in the bending surface region.

Various electrode assembly structures according to an embodiment of thepresent disclosure may be applied to a cylindrical battery.

Preferably, the cylindrical battery may be, for example, a cylindricalbattery whose form factor ratio (defined as a value obtained by dividingthe diameter of the cylindrical battery by height, namely a ratio ofheight (H)-to-diameter (Φ)) is greater than about 0.4. Here, the formfactor means a value indicating the diameter and height of a cylindricalbattery.

Preferably, the cylindrical battery may have a diameter of 40 mm to 50mm and a height of 60 mm to 130 mm. The form factor of the cylindricalbattery according to an embodiment of the present disclosure may be, forexample, 46110, 4875, 48110, 4880, or 4680. In the numerical valuerepresenting the form factor, first two numbers indicate the diameter ofthe battery and remaining numbers indicate the height of the battery.

When an electrode assembly having a tab-less structure is applied to acylindrical battery having a form factor ratio of more than 0.4, thestress applied in the radial direction when the uncoated portion is bentis large, so that the uncoated portion may be easily torn. In addition,when welding the current collector to the bent surface region of theuncoated portion, it is necessary to sufficiently increase the number ofoverlapping layers of the uncoated portion on the bent surface region inorder to sufficiently secure the welding strength and lower theresistance. This requirement may be achieved by the electrode and theelectrode assembly according to the embodiments (modifications) of thepresent disclosure.

A battery according to an embodiment of the present disclosure may be acylindrical battery having an approximately cylindrical shape, whosediameter is approximately 46 mm, height is approximately 110 mm, andform factor ratio is 0.418.

A battery according to another embodiment may be a cylindrical batteryhaving a substantially cylindrical shape, whose diameter is about 48 mm,height is about 75 mm, and form factor ratio is 0.640.

A battery according to still another embodiment may be a cylindricalbattery having an approximately cylindrical shape, whose diameter isapproximately 48 mm, height is approximately 110 mm, and form factorratio is 0.436.

A battery according to still another embodiment may be a cylindricalbattery having an approximately cylindrical shape, whose diameter isapproximately 48 mm, height is approximately 80 mm, and form factorratio is 0.600.

A battery according to still another embodiment may be a cylindricalbattery having an approximately cylindrical shape, whose diameter isapproximately 46 mm, height is approximately 80 mm, and form factorratio is 0.575.

Conventionally, batteries having a form factor ratio of about 0.4 orless have been used. That is, conventionally, for example, 1865 battery,2170 battery, etc. were used. The 1865 battery has a diameter ofapproximately 18 mm, height of approximately 65 mm, and a form factorratio of 0.277. The 2170 battery has a diameter of approximately 21 mm,a height of approximately 70 mm, and a form factor ratio of 0.300.

Hereinafter, the cylindrical battery according to an embodiment of thepresent disclosure will be described in detail.

FIG. 17 is a sectional view showing a cylindrical battery 140 accordingto an embodiment of the present disclosure, taken along the Y-axisdirection.

Referring to FIG. 17 , the cylindrical battery 140 according to anembodiment of the present disclosure includes an electrode assembly 141having a first electrode, a separator and a second electrode, a batteryhousing 142 for accommodating the electrode assembly 141, and a sealingbody 143 for sealing an open end of the battery housing 142.

The battery housing 142 is a cylindrical container with an opening atthe top. The battery housing 142 is made of a conductive metal materialsuch as aluminum, steel or stainless steel. A nickel coating layer maybe formed on the surface of the battery housing 142. The battery housing142 accommodates the electrode assembly 141 in the inner space throughthe top opening and also accommodates the electrolyte.

The electrolyte may be a salt having a structure like A⁺B⁻. Here, A⁺includes an alkali metal cation such as Li⁺, Na⁺, or K⁺, or acombination thereof. and B⁻ includes at least one anion selected fromthe group consisting of F⁻, Cl⁻, Br⁻, I⁻, NO₃ ⁻, N (CN)₂ ⁻, BF₄ ⁻, ClO₄⁻, AlO₄ ⁻, AlCl₄ ⁻, PF₆ ⁻, SbF₆ ⁻, AsF₆ ⁻, BF₂C₂O₄ ⁻, BC₄O₈ ⁻, (CF₃)₂PF₄⁻, (CF₃)₃PF₃ ⁻, (CF₃)₄PF₂, (CF₃)₅PF⁻, (CF₃)₆P⁻, CF₃SO₃ ⁻, C₄F₉SO₃ ⁻,CF₃CF₂SO₃ ⁻, (CF₃SO₂)₂N⁻, (FSO₂)₂N⁻, CF₃CF₂ (CF₃)₂CO⁻, (CF₃SO₂)₂CH⁻,(SF₅)₃C⁻, (CF₃SO₂)₃C⁻, CF₃ (CF₂)₇SO₃ ⁻, CF₃CO₂, CH₃CO₂ ⁻, SCN⁻ and(CF₃CF₂SO₂)₂N⁻.

The electrolyte may also be dissolved in an organic solvent. The organicsolvent may employ propylene carbonate (PC), ethylene carbonate (EC),diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate(DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane,diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), γ-butyrolactone, or a mixture thereof.

The electrode assembly 141 may have a jelly-roll shape but the presentinvention is not limited thereto. The electrode assembly 141 may bemanufactured by winding a laminate formed by sequentially laminating alower separator, a first electrode, an upper separator, and a secondelectrode at least once, based on the winding axis of the core C, asshown in FIG. 2 .

The first electrode and the second electrode have different polarities.That is, if one has positive polarity, the other has negative polarity.At least one of the first electrode and the second electrode may have anelectrode structure according to the above embodiments (modifications).In addition, the other of the first electrode and the second electrodemay have a conventional electrode structure or an electrode structureaccording to embodiments (modifications). The electrode pair included inthe electrode assembly 141 is not limited to one pair, but two or morepairs may also be included.

A first uncoated portion 146 a of the first electrode and a seconduncoated portion 146 b of the second electrode protrude from the upperand lower portions of the electrode assembly 141, respectively. Thefirst electrode has the electrode structure of the first embodiment(modification). Accordingly, in the first uncoated portion 146 a, theheight of the second part B3 is smaller than the height of the uncoatedportion of the other region. The second part B3 is spaced apart from theinner circumference of the battery housing 142, particularly the beadingportion 147, with a predetermined interval. Therefore, the second partB3 of the first electrode does not come into contact with the batteryhousing 142 electrically connected to the second electrode, therebypreventing an internal short circuit of the battery 140.

The second uncoated portion 146 b of the second electrode may have thesame structure as the first uncoated portion 146 a. In anothermodification, the second uncoated portion 146 b may optionally have thestructure of the uncoated portion of the electrode according toembodiments (modifications).

The sealing body 143 may include a cap 143 a having a plate shape, afirst gasket 143 b for providing airtightness between the cap 143 a andthe battery housing 142 and having insulation property, and a connectionplate 143 c electrically and mechanically coupled to the cap 143 a.

The cap 143 a is a component made of a conductive metal material, andcovers the top opening of the battery housing 142. The cap 143 a iselectrically connected to the uncoated portion 146 a of the firstelectrode, and is electrically insulated from the battery housing 142 bymeans of the first gasket 143 b. Accordingly, the cap 143 a may functionas a first electrode terminal (for example, the positive electrode) ofthe cylindrical battery 140.

The cap 143 a is placed on the beading portion 147 formed on the batteryhousing 142, and is fixed by a crimping portion 148. Between the cap 143a and the crimping portion 148, the first gasket 143 b may be interposedto secure the airtightness of the battery housing 142 and the electricalinsulation between the battery housing 142 and the cap 143 a. The cap143 a may have a protrusion 143 d protruding upward from the centerthereof.

The battery housing 142 is electrically connected to the second uncoatedportion 146 b of the second electrode. Therefore, the battery housing142 has the same polarity as the second electrode. If the secondelectrode has negative polarity, the battery housing 142 also hasnegative polarity.

The battery housing 142 includes the beading portion 147 and thecrimping portion 148 at the top thereof. The beading portion 147 isformed by press-fitting the periphery of the outer circumference of thebattery housing 142. The beading portion 147 prevents the electrodeassembly 141 accommodated inside the battery housing 142 from escapingthrough the top opening of the battery housing 142, and may function asa support portion on which the sealing body 143 is placed.

The inner circumference of the beading portion 147 is spaced apart fromthe second part B3 of the first electrode with a predetermined interval.More specifically, the lower end of the inner circumference of thebeading portion 147 is spaced apart from the second part B3 of the firstelectrode with a predetermined interval. In addition, since the secondpart B3 has a low height, the second part B3 is not substantiallyaffected even when the battery housing 142 is press-fitted from theoutside to form the beading portion 147. Accordingly, the second part B3is not compressed by other components such as the beading portion 147,and thus the shape of the electrode assembly 141 is prevented from beingpartially deformed, thereby preventing a short circuit inside thecylindrical battery 140.

Preferably, when the press-in depth of the beading portion 147 isdefined as D1 and the radial length from the inner circumference of thebattery housing 142 to the boundary point of the second part B3 and thethird part B2 is defined as D2, the formula D1≤D2 may be satisfied. Inthis case, damage to the second part B3 is substantially prevented whenthe battery housing is press-fitted to form the beading portion 147.

The crimping portion 148 is formed on the beading portion 147. Thecrimping portion has an extended and bent shape to cover the outercircumference of the cap 143 a disposed on the beading portion 147 and apart of the upper surface of the cap 143 a.

The cylindrical battery 140 may further include a first currentcollector 144 and/or a second current collector 145 and/or an insulator146.

The first current collector 144 is coupled to the upper portion of theelectrode assembly 141. The first current collector 144 is made of aconductive metal material such as aluminum, copper, steel and nickel,and is electrically connected to the uncoated portion 146 a of the firstelectrode. The electric connection may be performed by welding. A lead149 may be connected to the first current collector 144. The lead 149may extend upward above the electrode assembly and be coupled to theconnection plate 143 c or directly coupled to the lower surface of thecap 143 a. The lead 149 may be connected to other components by welding.

Preferably, the first current collector 144 may be integrally formedwith the lead 149. In this case, the lead 149 may have an elongatedplate shape extending outward from the vicinity of the center of thefirst current collector 144.

The first current collector 144 may include a plurality of unevennessradially formed on a lower surface thereof. When the radial unevennessis provided, the unevenness may be press-fitted into the first uncoatedportion 146 a of the first electrode by pressing the first currentcollector 144.

The first current collector 144 is coupled to the end of the firstuncoated portion 146 a. The first uncoated portion 146 a and the firstcurrent collector 144 may be coupled, for example, by laser welding.Laser welding may be performed in a manner that partially melts a basematerial of the current collector 144. In a modification, the firstcurrent collector 144 and the first uncoated portion 146 a may be weldedin a state where a solder is interposed therebetween. In this case, thesolder may have a lower melting point compared to the first currentcollector 144 and the first uncoated portion 146 a. Laser welding may bereplaced by resistance welding, ultrasonic welding, spot welding, or thelike.

The second current collector 145 may be coupled to the lower surface ofthe electrode assembly 141. One side of the second current collector 145may be coupled to the second uncoated portion 146 b by welding, and theother side may be coupled to the inner bottom surface of the batteryhousing 142 by welding. The coupling structure between the secondcurrent collector 145 and the second uncoated portion 146 b may besubstantially the same as the coupling structure between the firstcurrent collector 144 and the first uncoated portion 146 a.

The uncoated portions 146 a, 146 b are not limited to the illustratedstructure. Accordingly, the uncoated portions 146 a, 146 b mayselectively adopt not only a conventional uncoated portion structure butalso the uncoated portion structure of the electrode according toembodiments (modifications).

The insulator 146 may cover the first current collector 144. Theinsulator 146 may cover the first current collector 144 at the uppersurface of the first current collector 144, thereby preventing directcontact between the first current collector 144 and the innercircumference of the battery housing 142.

The insulator 146 has a lead hole 151 so that the lead 149 extendingupward from the first current collector 144 may be withdrawntherethrough. The lead 149 is drawn upward through the lead hole 151 andcoupled to the lower surface of the connection plate 143 c or the lowersurface of the cap 143 a.

A peripheral region of the edge of the insulator 146 may be interposedbetween the first current collector 144 and the beading portion 147 tofix the coupled body of the electrode assembly 141 and the first currentcollector 144. Accordingly, in the coupled body of the electrodeassembly 141 and the first current collector 144, the movement of thebattery 140 in the winding axis direction Y may be restricted, therebyimproving the assembly stability of the battery 140.

The insulator 146 may be made of an insulating polymer resin. In oneexample, the insulator 146 may be made of polyethylene, polypropylene,polyimide, or polybutylene terephthalate.

The battery housing 142 may further include a venting portion 152 formedat a lower surface thereof. The venting portion 152 corresponds to aregion having a smaller thickness compared to the peripheral region ofthe lower surface of the battery housing 142. The venting portion 152 isstructurally weak compared to the surrounding area. Accordingly, when anabnormality occurs in the cylindrical battery 140 and the internalpressure increases to a predetermined level or more, the venting portion152 may be ruptured so that the gas generated inside the battery housing142 is discharged to the outside. The internal pressure at which theventing portion 152 ruptures may be approximately 15 kgf/cm² to 35kgf/cm².

The venting portion 152 may be formed continuously or discontinuouslywhile drawing a circle at the lower surface of the battery housing 142.In a modification, the venting portion may be formed in a straightpattern or other patterns.

FIG. 18 is a sectional view showing a cylindrical battery 150 accordingto another embodiment of the present disclosure, taken along the Y-axisdirection.

Referring to FIG. 18 , the cylindrical battery 150 is substantially thesame as the cylindrical battery 140 of FIG. 17 , except that theelectrode structure of the second embodiment (modification) is employedin the first uncoated portion 146 a of the first electrode.

Referring to FIG. 18 , the first uncoated portion 146 a of the firstelectrode may have a shape in which the height of the second part B3 isdecreased gradually or stepwise toward the inner circumference of thebattery housing 142. Preferably, the virtual line connecting the top endof the second part B3 may have the same or similar shape as the innercircumference of the beading portion 147.

The second part B3 forms an inclined surface. Accordingly, when thebattery housing is press-fitted to form the beading portion 147, it ispossible to prevent the second part B3 from being compressed and damagedby the beading portion 147. In addition, it is possible to suppress thephenomenon that the second part B3 comes into contact with the batteryhousing having a different polarity to cause an internal short circuit.

The remaining components of the cylindrical battery 150 aresubstantially the same as the embodiment (modification) described above.

The uncoated portions 146 a, 146 b are not limited to the illustratedstructure. Accordingly, the uncoated portions 146 a, 146 b mayselectively have not only a conventional uncoated portion structure butalso the uncoated portion structure of the electrode according toembodiments (modifications).

FIG. 19 is a sectional view showing a cylindrical battery 160 accordingto still another embodiment of the present disclosure, taken along theY-axis direction.

Referring to FIG. 19 , the cylindrical battery 160 is substantially thesame as the cylindrical batteries 140, 150 described above, except thatthe lead 149 connected to the first current collector 144 is directlyconnected to the cap 143 a of the sealing body 143 through the lead hole151 of the insulator 146, and the insulator 146 and the first currentcollector 144 have a structure in close contact with the lower surfaceof the cap 143 a.

In the cylindrical battery 160, the diameter of the first currentcollector 144 and the outermost diameter of the third part B2 aresmaller than the minimum inner diameter of the battery housing 142.Also, the diameter of the first current collector 144 may be equal to orgreater than the outermost diameter of the third part B2.

Specifically, the minimum inner diameter of the battery housing 142 maycorrespond to the inner diameter of the battery housing 142 at aposition where the beading portion 147 is formed. At this time, theoutermost diameter of the first current collector 144 and the third partB2 is smaller than the inner diameter of the battery housing 142 at theposition where the beading portion 147 is formed. Also, the diameter ofthe first current collector 144 may be equal to or greater than theoutermost diameter of the third part B2. The peripheral region of theedge of the insulator 146 may be interposed between the second part B3and the beading portion 147 in a state of being bent downward to fix thecoupled body of the electrode assembly 141 and the first currentcollector 144.

Preferably, the insulator 146 may include a portion covering the secondpart B3 and a portion covering the first current collector 144, and aportion connecting these two portions may have a form curved together inresponse to the curved shape of the beading portion 147. The insulator146 may insulate the second part B3 and the inner circumference of thebeading portion and at the same time insulate the first currentcollector 144 and the inner circumference of the beading portion 147.

The first current collector 144 may be positioned higher than the lowerend of the beading portion 147, and may be coupled to the first part B1and the third part B2. At this time, the press-in depth D1 of thebeading portion 147 is less than or equal to the distance D2 from theinner circumference of the battery housing 142 to the boundary betweenthe second part B3 and the third part B2. Accordingly, the first partB1, the third part B2, and the first current collector coupled theretomay be positioned higher than the lower end of the beading portion 147.The lower end of the beading portion 147 means a bending point (B)between the portion of the battery housing 142 in which the electrodeassembly 141 is accommodated and the beading portion 147.

Since the first part B1 and the third part B2 occupy the inner space ofthe beading portion 147 in the radial direction, an empty space betweenthe electrode assembly 141 and the cap 143 a may be minimized. Inaddition, the connection plate 143 c located in the empty space betweenthe electrode assembly 141 and the cap 143 a is omitted. Accordingly,the lead 149 of the first current collector 144 may be directly coupledto the lower surface of the cap 143 a. According to the above structure,an empty space in the battery may be reduced, and the energy density maybe maximized as much as the reduced empty space.

In the cylindrical battery 160, the first current collector 144 and thesecond current collector 145 may be welded to the ends of the first andsecond uncoated portions 146 a, 146 b, respectively, in the same manneras in the above embodiment.

The uncoated portions 146 a, 146 b are not limited to the illustratedstructure. Accordingly, the uncoated portions 146 a, 146 b mayselectively have not only a conventional uncoated portion structure butalso the uncoated portion structure of the electrode according toembodiments (modifications).

FIG. 20 is a sectional view showing a cylindrical battery 170 accordingto still another embodiment of the present disclosure, taken along theY-axis.

Referring to FIG. 20 , the structure of the electrode assembly of thecylindrical battery is substantially the same as that of the cylindricalbattery 140 of in FIG. 17 , and the other structure except for theelectrode assembly is changed.

Specifically, the cylindrical battery 170 includes a battery housing 171through which a terminal 172 is installed. The terminal 172 is installedthrough a perforation hole formed in the closed surface (the uppersurface in the drawing) of the battery housing 171. The terminal 172 isriveted to the perforation hole of the battery housing 171 in a statewhere a second gasket 173 made of an insulating material is interposedtherebetween. The terminal 172 is exposed to the outside in a directionopposite to the direction of gravity.

The terminal 172 includes a terminal exposing portion 172 a and aterminal insert portion 172 b. The terminal exposing portion 172 a isexposed to the outside of the closed surface of the battery housing 171.The terminal exposing portion 172 a may be located approximately at acentral portion of the closed surface of the battery housing 171. Themaximum diameter of the terminal exposing portion 172 a may be largerthan the maximum diameter of the perforation hole formed in the batteryhousing 171. The terminal insert portion 172 b may be electricallyconnected to the uncoated portion 146 a of the first electrode throughapproximately the central portion of the closed surface of the batteryhousing 171. The bottom edge of the terminal insert portion 172 b may beriveted onto the inner surface of the battery housing 171. That is, thebottom edge of the terminal insert portion 172 b may have a shape curvedtoward the inner surface of the battery housing 171. A flat portion 172c is included inside the bottom edge of the terminal insert portion 172b. The maximum diameter of the riveted lower portion of the terminalinsert portion 172 b may be larger than the maximum diameter of theperforation hole of the battery housing 171.

The flat portion 172 c of the terminal insert portion 172 b may bewelded to the center of the first current collector 144 connected to thefirst uncoated portion 146 a of the first electrode. As the weldingmethod, laser welding is preferred, but other welding methods such asultrasonic welding may be used.

An insulator 174 made of an insulating material may be interposedbetween the first current collector 144 and the inner surface of thebattery housing 171. The insulator 174 covers the upper portion of thefirst current collector 144 and the top edge of the electrode assembly141. Accordingly, it is possible to prevent the second part B3 of theelectrode assembly 141 from contacting the inner surface of the batteryhousing 171 having a different polarity to cause a short circuit.

The thickness of the insulator 174 corresponds to or is slightly largerthan the distance between the upper surface of the first currentcollector 144 and the inner surface of the closed portion of the batteryhousing 171. Accordingly, the insulator 174 may be in contact with theupper surface of the first current collector 144 and the inner surfaceof the closed portion of the battery housing 171.

The terminal insert portion 172 b of the terminal 172 may be welded tothe first current collector 144 through the perforation hole of theinsulator 174. The diameter of the perforation hole formed in theinsulator 174 may be larger than the diameter of the riveting portion atthe lower end of the terminal insert portion 172 b. Preferably, theperforation hole may expose the lower portion of the terminal insertportion 172 b and the second gasket 173.

The second gasket 173 is interposed between the battery housing 171 andthe terminal to prevent the battery housing 171 and the terminal 172having opposite polarities from electrically contacting each other.Accordingly, the upper surface of the battery housing 171 having anapproximately flat shape may function as a second electrode terminal(for example, the negative electrode) of the cylindrical battery 170.

The second gasket 173 includes a gasket exposing portion 173 a and agasket insert portion 173 b. The gasket exposing portion 173 a isinterposed between the terminal exposing portion 172 a of the terminal172 and the battery housing 171. The gasket insert portion 173 b isinterposed between the terminal insert portion 172 b of the terminal 172and the battery housing 171. The gasket insert portion 173 b may bedeformed together when the terminal insert portion 172 b is riveted, soas to be in close contact with the inner surface of the battery housing171. The second gasket 173 may be made of, for example, a polymer resinhaving insulation.

The gasket exposing portion 173 a of the second gasket 173 may have anextended shape to cover the outer circumference of the terminal exposingportion 172 a of the terminal 172. When the second gasket 173 covers theouter circumference of the terminal 172, it is possible to prevent ashort circuit from occurring while an electrical connection part such asa bus bar is coupled to the upper surface of the battery housing 171and/or the terminal 172. The gasket exposing portion 173 a may have anextended shape to cover not only the outer circumference surface of theterminal exposing portion 172 a but also a part of the upper surfacethereof.

When the second gasket 173 is made of a polymer resin, the second gasket173 may be coupled to the battery housing 171 and the terminal 172 bythermal fusion. In this case, airtightness at the coupling interfacebetween the second gasket 173 and the terminal 172 and at the couplinginterface between the second gasket 173 and the battery housing 171 maybe enhanced. Meanwhile, when the gasket exposing portion 173 a of thesecond gasket 173 has a shape extending to the upper surface of theterminal exposing portion 172 a, the terminal 172 may be integrallycoupled with the second gasket 173 by insert injection molding.

In the upper surface of the battery housing 171, a remaining area 175other than the area occupied by the terminal 172 and the second gasket173 corresponds to the second electrode terminal having a polarityopposite to that of the terminal 172.

The second current collector 176 is coupled to the lower portion of theelectrode assembly 141. The second current collector 176 is made of aconductive metal material such as aluminum, steel, copper or nickel, andis electrically connected to the second uncoated portion 146 b of thesecond electrode.

Preferably, the second current collector 176 is electrically connectedto the battery housing 171. To this end, at least a portion of the edgeof the second current collector 176 may be interposed and fixed betweenthe inner surface of the battery housing 171 and a first gasket 178 b.In one example, at least a portion of the edge of the second currentcollector 176 may be fixed to the beading portion 180 by welding in astate of being supported on the bottom surface of the beading portion180 formed at the bottom of the battery housing 171. In a modification,at least a portion of the edge of the second current collector 176 maybe directly welded to the inner wall surface of the battery housing 171.

The second current collector 176 may include a plurality of unevenness)radially formed on a surface facing the second uncoated portion 146 b.When the unevenness is formed, the unevenness may be press-fitted intothe second uncoated portion 146 b by pressing the second currentcollector 176.

Preferably, the second current collector 176 and the ends of the seconduncoated portion 146 b may be coupled by welding, for example, laserwelding. In addition, the welding portions of the second currentcollector 176 and the second uncoated portion 146 b may be spaced apartby a predetermined distance toward the core C based on the innercircumference of the beading portion 180.

A sealing body 178 for sealing the lower open end of the battery housing171 includes a cap 178 a having a plate shape and a first gasket 178 b.The first gasket 178 b electrically separates the cap 178 a and thebattery housing 171. A crimping portion 181 fixes the edge of the cap178 a and the first gasket 178 b together. The cap 178 a has a ventingportion 179. The configuration of the venting portion 179 issubstantially the same as the above embodiment (modification). The lowersurface of the cap 178 a may be located higher than the lower end of thecrimping portion 181. In this case, a space is formed below the cap 178a, thereby securing smooth venting. This is particularly useful when thecylindrical battery 170 is installed so that the crimping portion 181faces the direction of gravity.

Preferably, the cap 178 a is made of a conductive metal material.However, since the first gasket 178 b is interposed between the cap 178a and the battery housing 171, the cap 178 a does not have electricalpolarity. The sealing body 178 mainly seals the open end of the lowerportion of the battery housing 171 and functions to discharge gas whenthe internal pressure of the battery 170 increases over a criticalvalue. The critical value of the internal pressure is 15 kgf/cm² to 35kgf/cm².

Preferably, the terminal 172 electrically connected to the firstuncoated portion 146 a of the first electrode is used as the firstelectrode terminal. In addition, in the upper surface of the batteryhousing 171 electrically connected to the second uncoated portion 146 bof the second electrode through the second current collector 176, a part175 except for the terminal 172 is used as the second electrode terminalhaving a different polarity from the first electrode terminal. If twoelectrode terminals are located at the upper portion of the cylindricalbattery 170 as above, it is possible to arrange electrical connectioncomponents such as bus bars at only one side of the cylindrical battery170. This may bring about simplification of the battery pack structureand improvement of energy density. In addition, since the part 175 usedas the second electrode terminal has an approximately flat shape, asufficient connecting area may be secured for connecting electricalconnection components such as bus bars. Accordingly, the cylindricalbattery 170 may reduce the resistance at the connection portion of theelectrical connection components to a desirable level.

Meanwhile, the structure of the uncoated portion and the structure ofthe electrode assembly 141 are not limited to those shown in thedrawings, and may be replaced with the structures of the aboveembodiments (modifications).

FIG. 21 is a sectional view showing a cylindrical battery 180 accordingto still another embodiment of the present disclosure, taken along theY-axis.

Referring to FIG. 21 , the structure of the electrode assembly 141 ofthe cylindrical battery 180 is substantially the same as that of thecylindrical battery 150 illustrated in FIG. 18 , and the componentsother than the electrode assembly 141 are substantially the same as thecylindrical battery 170 shown in FIG. 20 .

Accordingly, the configuration of the embodiment (modification) withrespect to the cylindrical batteries 150, 170 may be equally applied tothe cylindrical battery 180.

In addition, the structure of the electrode assembly 141 and thestructure of the uncoated portion are not limited to those shown in thedrawing, and may be replaced with the structures of the aboveembodiments (modifications).

FIG. 22 is a sectional view showing a cylindrical battery 190 accordingto still another embodiment of the present disclosure, taken along theY-axis.

Referring to FIG. 22 , the cylindrical battery 190 includes theelectrode assembly 110 illustrated in FIG. 14 , and the components otherthan the electrode assembly 110 are substantially the same as thecylindrical battery 140 illustrated in FIG. 17 . Accordingly, theconfiguration described with reference to FIGS. 14 and 17 may be appliedsubstantially in the same manner to this embodiment.

Referring to FIGS. 10 a and 22, the first and second uncoated portions146 a, 146 b of the electrode assembly 110 are bent in the radialdirection of the electrode assembly 110, for example from the outercircumference to the core to form a bending surface region F.

The first part B1 has a lower height than the other portions andcorresponds to the segment skip region a1 having no segment, so it isnot bent toward the core.

Preferably, the bending surface region F may include a segment skipregion a1, a height variable region a2 of the segment, and a heightuniform region a3 of the segment from the core toward the outercircumference.

As shown in FIGS. 10 c, 10 d and 10 e , the bending surface region Fincludes an overlapping layer number uniform region b1 adjacent to thesegment skip region a1, in which the number of overlapping layers ofsegments is 10 or more.

The bending surface region F may also include an overlapping layernumber decreasing region b2 adjacent to the outer circumference of theelectrode assembly 110, in which the number of overlapping layers ofsegments gradually decreases toward the outer circumference. Preferably,the overlapping layer number uniform region b1 may be set as the weldingtarget region.

In the bending surface region F, the preferable numerical ranges of theratio (a2/c) which is a ratio of the height variable region a2 to theradius region c including segments, the ratio (b1/c) of the overlappinglayer number uniform region b1 to the radius region c includingsegments, and the ratio of the area of the overlapping layer numberuniform region b1 to the area of the bending surface region F arealready described above, and thus will not be described again.

The first current collector 144 may be laser-welded to the bendingsurface region F of the first uncoated portion 146 a, and the secondcurrent collector 145 may be laser-welded to the bending surface regionF of the second uncoated portion 146 b. The welding method may bereplaced by ultrasonic welding, resistance welding, spot welding, or thelike.

Preferably, 50% or more of the welding region W of the first currentcollector 144 and the second current collector 145 may overlap with theoverlapping layer number uniform region b1 of the bending surface regionF. Optionally, the remaining region of the welding region W may overlapwith the overlapping layer number decreasing region b2 of the bendingsurface region F. In terms of high welding strength, low resistance ofthe welding interface, and prevention of damage to the separator or theactive material layer, it is more preferable that the entire weldingregion W overlaps with the overlapping layer number uniform region b1.

Preferably, in the overlapping layer number uniform region b1overlapping with the welding region W and, optionally, the overlappinglayer number decreasing region b2, the number of overlapping layers ofsegments may be 10 to 35.

Optionally, when the number of overlapping layers of segments in theoverlapping layer number decreasing region b2 overlapping with thewelding region W is less than 10, the laser power for welding theoverlapping layer number decreasing region b2 may be lowered below thatof the overlapping layer number uniform region b1. That is, when thewelding region W overlaps with the overlapping layer number uniformregion b1 and the overlapping layer number decreasing region b2 at thesame time, the laser power may be varied according to the number ofoverlapping layers of segments. In this case, the welding strength ofthe overlapping layer number uniform region b1 may be greater than thewelding strength of the overlapping layer number decreasing region b2.

In the bending surface region F formed at the upper and lower portionsof the electrode assembly 110, the radial length of the segment skipregion a1 and/or the height variable region a2 of the segment and/or theheight uniform region a3 of the segment may be the same or differentfrom each other.

In the electrode assembly 110, the height of the first part B1 isrelatively smaller than that of the other portions. Also, as shown inFIG. 14 , the bending length (H) of the uncoated portion located at theinnermost side of the third part B2 is smaller than a value obtained byadding the radial length (R) of the first part B1 and 10% of the radiusof the core 112.

Accordingly, even when the first uncoated portion 146 a is bent towardthe core, the core of the electrode assembly 110 may be opened to theoutside by at least 90% or more of its diameter. If the core 112 is notblocked, there is no difficulty in the electrolyte injection process andthe electrolyte injection efficiency is improved. In addition, byinserting a welding jig through the core 112, the welding processbetween the second current collector 145 and the battery housing 142 maybe easily performed.

When the uncoated portions 146 a, 146 b have a segment structure, if thewidth and/or height and/or separation pitch of the segments are adjustedto satisfy the numerical ranges of the above embodiment, the segmentsare overlapped in multiple layers to sufficiently secure weldingstrength when the segments are bent, and an empty space (gap) is notformed in the bent surface region F.

Preferably, the first current collector 144 and the second currentcollector 145 may have an outer diameter covering the ends of thesegments 61, 61′ (see FIG. 10 f ) bent in the last winding turn of theheight uniform region a3 of the first electrode and the secondelectrode. In this case, welding may be performed in a state where thesegments forming the bending surface region F are uniformly pressed bythe current collector, and the tightly stacked state of the segments maybe maintained well even after welding. The tightly stacked state means astate in which there are substantially no gaps between the segments asshown in FIG. 10 a . The tightly stacked state contributes to loweringthe resistance of the cylindrical battery 190 to a level suitable forrapid charging (e.g., 4 milliohms) or below.

The structures of the uncoated portions 146 a, 146 b may be changed tothe structures according to the above embodiments (modifications). Inaddition, a conventional uncoated portion structure may be applied toany one of the uncoated portions 146 a, 146 b without limitation.

FIG. 23 is a sectional view showing a cylindrical battery 200 accordingto still another embodiment of the present disclosure, taken along theY-axis.

Referring to FIG. 23 , the cylindrical battery 200 includes theelectrode assembly 110 illustrated in FIG. 14 , and the components otherthan the electrode assembly 110 are substantially the same as those ofthe cylindrical battery 180 illustrated in FIG. 21 . Accordingly, theconfiguration described with reference to FIGS. 14 and 21 may be appliedsubstantially in the same manner to this embodiment.

Referring to FIGS. 10 a and 23, the first and second uncoated portions146 a, 146 b of the electrode assembly 110 are bent in the radialdirection of the electrode assembly 110, for example from the outercircumference toward the core, to form a bending surface region F.

The first part B1 has a lower height than the other portions andcorresponds to the segment skip region a1 having to segment, so it isnot bent toward the core.

Preferably, the bending surface region F may include a segment skipregion a1, a height variable region a2 of the segment, and a heightuniform region a3 of the segment from the core toward the outercircumference.

As shown in FIGS. 10 c, 10 d and 10 e , the bending surface region Fincludes an overlapping layer number uniform region b1 adjacent to thesegment skip region a1, in which the number of overlapping layers ofsegments is 10 or more.

The bending surface region F may also include an overlapping layernumber decreasing region b2 adjacent to the outer circumference of theelectrode assembly 110, in which the number of overlapping layers ofsegments decreases toward the outer circumference. Preferably, theoverlapping layer number uniform region b1 may be set as the weldingtarget region.

In the bending surface region F, the preferable numerical ranges of theratio (a2/c) which is a ratio of the height variable region a2 to aradius region c including segments, the ratio (b1/c) of the overlappinglayer number uniform region b1 to the radius region c includingsegments, and the ratio of the area of the overlapping layer numberuniform region b1 to the area of the bending surface region F arealready described above, and thus will not be described again.

The first current collector 144 may be laser-welded to the bendingsurface region F of the first uncoated portion 146 a, and the secondcurrent collector 176 may be laser-welded to the bending surface regionF of the second uncoated portion 146 b. The welding method may bereplaced by ultrasonic welding, resistance welding, spot welding, or thelike. The welding region W of the second current collector 176 and thesecond uncoated portion 146 b may be spaced apart from the inner surfaceof the beading portion 180 by a predetermined distance.

Preferably, 50% or more of the welding region W of the first currentcollector 144 and the second current collector 176 may overlap with theoverlapping layer number uniform region b1 of the bending surface regionF. Optionally, the remaining region of the welding region W may overlapwith the overlapping layer number decreasing region b2 of the bendingsurface region F. In terms of high welding strength, low resistance ofthe welding interface, and prevention of damage to the separator or theactive material layer, it is more preferable that the entire weldingregion W overlaps with the overlapping layer number uniform region b1.

Preferably, in the overlapping layer number uniform region b1overlapping with the welding region W and, optionally, the overlappinglayer number decreasing region b2, the number of overlapping layers ofsegments may be 10 to 35.

Optionally, when the number of overlapping layers of segments in theoverlapping layer number decreasing region b2 overlapping with thewelding region W is less than 10, the laser power for welding theoverlapping layer number decreasing region b2 may be lowered below thatof the overlapping layer number uniform region b1. That is, when thewelding region W overlaps with the overlapping layer number uniformregion b1 and the overlapping layer number decreasing region b2 at thesame time, the laser power may be varied according to the number ofoverlapping layers of segments. In this case, the welding strength ofthe overlapping layer number uniform region b1 may be greater than thewelding strength of the overlapping layer number decreasing region b2.

In the bending surface region F formed at the upper and lower portionsof the electrode assembly 110, the radial length of the segment skipregion a1 and/or the height variable region a2 of the segment and/or theheight uniform region a3 of the segment may be the same or differentfrom each other.

In the electrode assembly 110, the height of the first part B1 isrelatively smaller than that of the other portions. Also, as shown inFIG. 14 , the bending length (H) of the uncoated portion located at theinnermost side of the third part B2 is smaller than a value obtained byadding the radial length (R) of the first part B1 and 10% of the radiusof the core 112.

Therefore, even when the uncoated portion 146 a is bent toward the core,the core 112 of the electrode assembly 110 may be opened to the outsideby at least 90% or more of its diameter. If the core 112 is not blocked,there is no difficulty in the electrolyte injection process and theelectrolyte injection efficiency is improved. In addition, by insertinga welding jig through the core 112, the welding process between thefirst current collector 144 and the terminal 172 may be easilyperformed.

When the first and second uncoated portions 146 a, 146 b have a segmentstructure, if the width and/or height and/or separation pitch of thesegments are adjusted to satisfy the numerical ranges of the aboveembodiment, the segments may be overlapped in multiple layers tosufficiently secure welding strength when the segments are bent, and anempty space (gap) is not formed in the bent surface region F.

Preferably, in the first current collector 144 and the second currentcollector 176, the regions contacting the first and second uncoatedportions 146 a, 146 may have an outer diameter covering the ends of thesegments 61, 61′ (see FIG. 10 f ) bent in the last winding turn of theheight uniform region a3 of the first electrode and the secondelectrode. In this case, welding may be performed in a state where thesegments forming the bending surface region F are uniformly pressed bythe current collector, and the tightly stacked state of the segments maybe maintained well even after welding. The tightly stacked state means astate in which there are substantially no gaps between the segments asshown in FIG. 10 a . The tightly stacked state contributes to loweringthe resistance of the cylindrical battery 190 to a level suitable forrapid charging (e.g., 4 milliohms) or below.

The structures of the uncoated portions 146 a, 146 b may be changed tothe structures according to the above embodiments (modifications). Inaddition, a conventional uncoated portion structure may be applied toany one of the uncoated portions 146 a, 146 b without limitation.

FIG. 24 is a cross-sectional view showing a cylindrical battery 210according to still another embodiment of the present disclosure, takenalong the Y-axis.

Referring to FIG. 24 , the cylindrical battery 210 includes theelectrode assembly 100 illustrated in FIG. 13 , and the configurationother than the electrode assembly 100 is substantially the same as thecylindrical battery 140 illustrated in FIG. 17 . Therefore, theconfiguration described with reference to FIGS. 13 and 17 may be appliedsubstantially identically in this embodiment.

Preferably, the first and second uncoated portions 146 a, 146 b of theelectrode assembly are divided into a plurality of segments, and theplurality of segments are bent in a radial direction of the electrodeassembly 100, for example from the outer circumference toward the core.At this time, the first part B1 and the second part B3 of the firstuncoated portion 146 a have a lower height than the other portions andhave no segment, and thus they are not substantially bent. This is thesame for the second uncoated portion 146 b.

Also in this embodiment, the bending surface region F may include asegment skip region a1, a height variable region a2 of the segment, anda height uniform region a3 of the segment from the core toward the outercircumference. However, since the second part B3 is not bent, the radiallength of the bending surface region F may be shorter than that of theformer embodiment.

As shown in FIGS. 10 c, 10 d and 10 e , the bending surface region Fincludes an overlapping layer number uniform region b1 adjacent to thesegment skip region a1, in which the number of overlapping layers ofsegments is 10 or more.

The bending surface region F may also include an overlapping layernumber decreasing region b2 adjacent to the second part B3 of theelectrode assembly 110, in which the number of overlapping layers ofsegments gradually decreases toward the outer circumference. Preferably,the overlapping layer number uniform region b1 may be set as the weldingtarget region.

In the bending surface region F, the preferable numerical ranges of theratio (a2/c) which is a ratio of the height variable region a2 to aradius region (c) including segments, the ratio (b1/c) of theoverlapping layer number uniform region b1 to the radius regionincluding segments (c), and the ratio of the area of the overlappinglayer number uniform region b1 to the area of the bending surface regionF are already described above, and thus will not be described again.

The first current collector 144 may be welded to the bending surfaceregion F of the first uncoated portion 146 a, and the second currentcollector 145 may be welded to the bending surface region F of thesecond uncoated portion 146 b.

The overlapping relationship of the overlapping layer number uniformregion b1 and the overlapping layer number decreasing region b2 with thewelding region W, the outer diameter of the first current collector 144and the second current collector 145, the configuration in which thefirst part B1 does not close the core by at least 10% or more of itsdiameter, and the like are substantially the same as described above.

Meanwhile, the second part B3 has no segment and has a height lower thanthat of the third part B2. Accordingly, when the first uncoated portion146 a is bent, the second part B3 is not substantially bent. Inaddition, since the second part B3 is sufficiently spaced apart from thebeading portion 147, it is possible to solve the problem that the secondpart B3 is damaged while the beading portion 147 is press-fitted.

The structures of the uncoated portions 146 a, 146 b may be changed tothe structures according to the above embodiments (modifications). Inaddition, a conventional uncoated portion structure may be applied toany one of the uncoated portions 146 a, 146 b without limitation.

FIG. 25 is a cross-sectional view showing a cylindrical battery 220according to still another embodiment of the present disclosure, takenalong the Y-axis.

Referring to FIG. 25 , the cylindrical battery 220 includes theelectrode assembly 100 illustrated in FIG. 24 , and the configurationother than the electrode assembly 100 is substantially the same as thecylindrical battery 180 illustrated in FIG. 21 . Therefore, theconfiguration described with reference to FIGS. 21 and 24 may be appliedsubstantially identically in this embodiment.

Preferably, the first and second uncoated portions 146 a, 146 b of theelectrode assembly are divided into a plurality of segments, and theplurality of segments are bent from the outer circumference toward thecore. At this time, the first part B1 and the second part B3 of thefirst uncoated portion 146 a have a lower height than the other portionsand have no segment, and thus they are not substantially bent. This isthe same for the second uncoated portion 146 b.

Therefore, in this embodiment, similar to the embodiment of FIG. 24 ,the bending surface region F may include a segment skip region a1, aheight variable region a2 of the segment, and a height uniform region a3of the segment from the core toward the outer circumference. However,since the second part B3 is not bent, the radial length of the bendingsurface region F may be shorter than that of the former embodiment.

As shown in FIGS. 10 c, 10 d and 10 e , the bending surface region Fincludes an overlapping layer number uniform region b1 adjacent to thesegment skip region a1, in which the number of overlapping layers ofsegments is 10 or more.

The bending surface region F may also include an overlapping layernumber decreasing region b2 adjacent to the second part B3 of theelectrode assembly 110, in which the number of overlapping layers ofsegments gradually decreases toward the outer circumference. Preferably,the overlapping layer number uniform region b1 may be set as the weldingtarget region.

In the bending surface region F, the preferable numerical ranges of theratio (a2/c) which is a ratio of the height variable region a2 to aradius region including segments (c), the ratio (b1/c) of theoverlapping layer number uniform region b1 to the radius region (c)including segments, and the ratio of the area of the overlapping layernumber uniform region b1 to the area of the bending surface region F arealready described above, and thus will not be described again.

The first current collector 144 may be welded to the bending surfaceregion F of the first uncoated portion 146 a, and the second currentcollector 176 may be welded to the bending surface region F of thesecond uncoated portion 146 b.

The overlapping relationship of the overlapping layer number uniformregion b1 and the overlapping layer number decreasing region b2 with thewelding region W, the outer diameter of the first current collector 144and the second current collector 176, the configuration in which thefirst part B1 does not close the core by at least 10% or more of itsdiameter, and the like are substantially the same as described above.

The structures of the uncoated portions 146 a, 146 b may be changed tothe structures according to the former embodiments (modifications). Inaddition, the conventional uncoated portion structure may be applied toany one of the uncoated portions 146 a, 146 b without limitation.

In the former embodiments (modified examples), the first currentcollector 144 and the second current collector 176 included in thecylindrical battery 170, 180, 200, 220 including the terminal 172 mayhave an improved structure as shown in FIGS. 26 and 27 .

The improved structure of the first current collector 144 and the secondcurrent collector may contribute to lowering the resistance of thecylindrical battery, improving the vibration resistance, and improvingthe energy density. In particular, the first current collector 144 andthe second current collector 176 are more effective when used in a largecylindrical battery in which a ratio of diameter to height is greaterthan 0.4.

FIG. 26 is a top plan view showing the structure of the first currentcollector 144 according to an embodiment of the present disclosure.

Referring to FIGS. 23 and 26 together, the first current collector 144may include an edge portion 144 a, a first uncoated portion couplingportion 144 b, and a terminal coupling portion 144 c. The edge portion144 a is disposed on the electrode assembly 110. The edge portion 144 amay have a substantially rim shape having an empty space (S_(open))formed therein. In the drawings of the present disclosure, only a casein which the edge portion 144 a has a substantially circular rim shapeis illustrated, but the present disclosure is not limited thereto. Theedge portion 144 a may have a substantially rectangular rim shape, ahexagonal rim shape, an octagonal rim shape, or other rim shapes, unlikethe illustrated one. The number of the edge portion 144 a may beincreased to two or more. In this case, another edge portion in a rimshape may be provided to the inner side of the edge portion 144 a.

The terminal coupling portion 144 c may have a diameter equal to orgreater than the diameter of the flat portion 172 c formed on the bottomsurface of the terminal 172 in order to secure a welding area forcoupling with the flat portion 172 c formed on the bottom surface of theterminal 172.

The first uncoated portion coupling portion 144 b extends inward fromthe edge portion 144 a and is coupled to the uncoated portion 146 athrough welding. The terminal coupling portion 144 c is spaced apartfrom the first uncoated portion coupling portion 144 b and is positionedinside the edge portion 144 a. The terminal coupling portion 144 c maybe coupled to the terminal 172 by welding. The terminal coupling portion144 c may be located, for example, approximately at the center of theinner space (S_(open)) surrounded by the edge portion 144 a. Theterminal coupling portion 144 c may be provided at a positioncorresponding to the hole formed in the core C of the electrode assembly110. The terminal coupling portion 144 c may be configured to cover thehole formed in the core C of the electrode assembly 110 so that the holeformed in the core C of the electrode assembly 110 is not exposed out ofthe terminal coupling portion 144 c. To this end, the terminal couplingportion 144 c may have a larger diameter or width than the hole formedin the core C of the electrode assembly 110.

The first uncoated portion coupling portion 144 b and the terminalcoupling portion 144 c may not be directly connected, but may bedisposed to be spaced apart from each other and indirectly connected bythe edge portion 144 a. Since the first current collector 144 has astructure in which the first uncoated portion coupling portion 144 b andthe terminal coupling portion 144 c are not directly connected to eachother but are connected through the edge portion 144 c as above, whenshock and/or vibration occurs at the cylindrical battery 200, it ispossible to disperse the shock applied to the coupling portion betweenthe first uncoated portion coupling portion 144 b and the first uncoatedportion 146 a and the coupling portion between the terminal couplingportion 144 c and the terminal 172. In the drawings of the presentdisclosure, only a case in which four first uncoated portion couplingportions 144 b are provided is illustrated, but the present disclosureis not limited thereto. The number of the first uncoated portioncoupling portions 144 b may be variously determined in consideration ofmanufacturing difficulty according to the complexity of the shape,electric resistance, the space (S_(open)) inside the edge portion 144 aconsidering electrolyte impregnation, and the like.

The first current collector 144 may further include a bridge portion 144d extending inward from the edge portion 144 a and connected to theterminal coupling portion 144 c. At least a part of the bridge portion144 d may have a smaller sectional area compared to the first uncoatedportion coupling portion 144 b and the edge portion 144 a. For example,at least a part of the bridge portion 144 d may be formed to have asmaller width and/or thickness compared to the first uncoated portioncoupling portion 144 b. In this case, the electric resistance increasesin the bridge portion 144 d. As a result, when a current flows throughthe bridge portion 144 d, the relatively large resistance causes a partof the bridge portion 144 d to be melted due to overcurrent heating.Accordingly, the overcurrent is irreversibly blocked. The sectional areaof the bridge portion 144 d may be adjusted to an appropriate level inconsideration of the overcurrent blocking function.

The bridge portion 144 d may include a taper portion 144 e whose widthis gradually decreased from the inner surface of the edge portion 144 atoward the terminal coupling portion 144 c. When the taper portion 144 eis provided, the rigidity of the component may be improved at theconnection portion between the bridge portion 144 d and the edge portion144 a. When the taper portion 144 e is provided, in the process ofmanufacturing the cylindrical battery 200, for example, a transferdevice and/or a worker may easily and safely transport the first currentcollector 144 and/or a coupled body of the first current collector 144and the electrode assembly by gripping the taper portion 144 e. That is,when the taper portion 144 e is provided, it is possible to preventproduct defects that may occur by gripping a portion where welding isperformed with other components such as the first uncoated portioncoupling portion 144 b and the terminal coupling portion 144 c.

The first uncoated portion coupling portion 144 b may be provided inplural. The plurality of first uncoated portion coupling portions 144 bmay be disposed substantially at regular intervals from each other inthe extending direction of the edge portion 144 a. An extension lengthof each of the plurality of first uncoated portion coupling portions 144b may be substantially equal to each other. The first uncoated portioncoupling portion 144 b may be coupled to the bending surface region F ofthe uncoated portion 146 a by laser welding. The welding may be replacedby ultrasonic welding, spot welding, or the like.

The welding pattern 144 f formed by welding between the first uncoatedportion coupling portion 144 b and the bending surface region F may havea structure to extend along the radial direction of the electrodeassembly 110. The welding pattern 144 f may be a line pattern or a dotarray pattern.

The welding pattern 144 f corresponds to the welding region. Therefore,the welding pattern 144 f preferably overlaps with the overlapping layernumber uniform region b1 of the bending surface region F by 50% or more.The welding pattern 144 f that does not overlap with the overlappinglayer number uniform region b1 may overlap with the overlapping layernumber decreasing region b2. The entire welding pattern 144 f mayoverlap with the overlapping layer number uniform region b1 of thebending surface region F. In the bending surface region F below theregion where the welding pattern 144 f is formed, the number ofoverlapping layers of segments is preferably 10 or more in theoverlapping layer number uniform region b1 and, optionally, theoverlapping layer number decreasing region b2.

The terminal coupling portion 144 c may be disposed to be surrounded bythe plurality of first uncoated portion coupling portions 144 b. Theterminal coupling portion 144 c may be coupled to the flat portion 172 cof the terminal 172 by welding. The bridge portion 144 d may bepositioned between a pair of first uncoated portion coupling portions144 b adjacent to each other. In this case, the distance from the bridgeportion 144 d to any one of the pair of first uncoated portion couplingportions 144 b along the extending direction of the edge portion 144 amay be substantially equal to the distance from the bridge portion 144 dto the other one of the pair of first uncoated portion coupling portions144 b along the extending direction of the edge portion 144 a. Theplurality of first uncoated portion coupling portions 144 b may beformed to have substantially the same sectional area. The plurality offirst uncoated portion coupling portions 144 b may be formed to havesubstantially the same width and thickness.

The bridge portion 144 d may be provided in plural. Each of theplurality of bridge portions 144 d may be disposed between a pair offirst uncoated portion coupling portions 144 b adjacent to each other.The plurality of bridge portions 144 d may be disposed substantially atregular intervals to each other in the extending direction of the edgeportion 144 a. A distance from each of the plurality of bridge portions144 d to one of the pair of first uncoated portion coupling portions 144b adjacent to each other along the extending direction of the edgeportion 144 a may be substantially equal to a distance from each of theplurality of the bridge portion 144 d to the other of the pair of firstuncoated portion coupling portion 144 b.

In the case where the first uncoated portion coupling portion 144 band/or the bridge portion 144 d is provided in plural as describedabove, if the distance between the first uncoated portion couplingportions 144 b and/or the distance between the bridge portions 144 dand/or the distance between the first uncoated portion coupling portion144 b and the bridge portion 144 d is uniformly formed, a currentflowing from the first uncoated portion coupling portion 144 b towardthe bridge portion 144 d or a current flowing from the bridge portion144 d toward the first uncoated portion coupling portion 144 b may besmoothly and uniformly formed.

The bridge portion 144 d may include a notching portion N formed topartially reduce a sectional area of the bridge portion 144 d. Thesectional area of the notching portion N may be adjusted, for example,by partially reducing the width and/or thickness of the bridge portion144 d. When the notching portion N is provided, electric resistance isincreased in the region where the notching portion N is formed, therebyenabling rapid current interruption when overcurrent occurs.

The notching portion N is preferably provided in a region correspondingto the overlapping layer number uniform region b1 of the electrodeassembly 110 in order to prevent substances generated during rupturingfrom flowing into the electrode assembly 110. This is because, in thisregion, the number of overlapping layers of the segments of the uncoatedportion 146 a is maintained to the maximum and thus the overlappedsegments may function as a mask.

The notching portion N may be surrounded by an insulating tape. Then,since the heat generated at the notching portion N is not dissipated tothe outside, the notching portion N may be ruptured more quickly when anovercurrent flows through the bridge portion 144 d.

FIG. 27 is a top plan view showing the structure of the second currentcollector 176 according to an embodiment of the present disclosure.

Referring to FIGS. 23 and 27 together, the second current collector 176is disposed below the electrode assembly 110. In addition, the secondcurrent collector 176 may be configured to electrically connect theuncoated portion 146 b of the electrode assembly 110 and the batteryhousing 171. The second current collector 176 is made of a metalmaterial with conductivity and is electrically connected to the bendingsurface region F of the uncoated portion 146 b. In addition, the secondcurrent collector 176 is electrically connected to the battery housing171. The edge portion of the second current collector 176 may beinterposed and fixed between the inner surface of the battery housing171 and the first gasket 178 b. Specifically, the edge portion of thesecond current collector 176 may be interposed between the lower surfaceof the beading portion 180 of the battery housing 171 and the firstgasket 178 b. However, the present disclosure is not limited thereto,and the edge portion of the second current collector 176 may be weldedto the inner wall surface of the battery housing 171 in a region wherethe beading portion 180 is not formed.

The second current collector 176 may include a support portion 176 adisposed below the electrode assembly 110, a second uncoated portioncoupling portion 176 b extending from the support portion 176 aapproximately along the radial direction of the electrode assembly 110and coupled to the bending surface region F of the uncoated portion 146b, and a housing coupling portion 176 c extending from the supportportion 176 a toward the inner surface of the battery housing 171approximately along an inclined direction based on the radial directionof the electrode assembly 110 and coupled to the inner surface of thebattery housing 171. The second uncoated portion coupling portion 176 band the housing coupling portion 176 c are indirectly connected throughthe support portion 176 a, and are not directly connected to each other.Therefore, when an external shock is applied to the cylindrical battery200 of the present disclosure, it is possible to minimize thepossibility of damage to the coupling portion of the second currentcollector 176 and the electrode assembly 110 and the coupling portion ofthe second current collector 176 and the battery housing 171. However,the second current collector of the present disclosure is not limited tothe structure where the second uncoated portion coupling portion 176 band the housing coupling portion 176 c are only indirectly connected.For example, the second current collector 176 may have a structure thatdoes not include the support portion 176 a for indirectly connecting thesecond uncoated portion coupling portion 176 b and the housing couplingportion 176 c and/or a structure in which the uncoated portion 146 b andthe housing coupling portion 176 c are directly connected to each other.

The support portion 176 a and the second uncoated portion couplingportion 176 b are disposed below the electrode assembly 110. The seconduncoated portion coupling portion 176 b is coupled to the bendingsurface region F of the uncoated portion 146 b. In addition to thesecond uncoated portion coupling portion 176 b, the support portion 176a may also be coupled to the uncoated portion 146 b. The second uncoatedportion coupling portion 176 b and the bending surface region F of theuncoated portion 146 b may be coupled by welding. The welding may bereplaced with ultrasonic welding, spot welding, or the like. The supportportion 176 a and the second uncoated portion coupling portion 176 b arelocated higher than the beading portion 180 when the beading portion 180is formed on the battery housing 171.

The support portion 176 a has a current collector hole 176 d formed at alocation corresponding to the hole formed at the core C of the electrodeassembly 110. The core C of the electrode assembly 110 and the currentcollector hole 176 d communicating with each other may function as apassage for inserting a welding rod for welding between the terminal 172and the terminal coupling portion 144 c of the first current collector144 or for irradiating a laser beam.

The current collector hole 176 d may have a radius of 0.5 r_(c) or morecompared to the radius (r_(c)) of the hole formed in the core C of theelectrode assembly 110. If the radius of the current collector hole 176d is 0.5 r_(c) to 1.0 r_(c), when a vent occurs in the cylindricalbattery 200, it is possible to prevent that the winding structure of theseparator or the electrodes near the core C of the electrode assembly110 is pushed out of the core C due to the vent pressure. When theradius of the current collector hole 176 d is greater than 1.0 r_(c),the core C is opened to the maximum, so the electrolyte may be easilyinjected during the electrolyte injection process.

When the second uncoated portion coupling portion 176 b is provided inplural, the plurality of second uncoated portion coupling portions 176 bmay have a shape extending approximately radially from the supportportion 176 a of the second current collector 176 toward the sidewall ofthe battery housing 171. The plurality of second uncoated portioncoupling portions 176 b may be positioned to be spaced apart from eachother along the periphery of the support portion 176 a.

The housing coupling portion 176 c may be provided in plural. In thiscase, the plurality of housing coupling portions 176 c may have a shapeextending approximately radially from the center of the second currentcollector 176 toward the sidewall of the battery housing 171.Accordingly, the electrical connection between the second currentcollector 176 and the battery housing 171 may be made at a plurality ofpoints. Since the coupling for electrical connection is made at aplurality of points, the coupling area may be maximized, therebyminimizing electric resistance. The plurality of housing couplingportions 176 c may be positioned to be spaced apart from each otheralong the periphery of the support portion 176 a. At least one housingcoupling portion 176 c may be positioned between the second uncoatedportion coupling portions 176 b adjacent to each other. The plurality ofhousing coupling portions 176 c may be coupled to, for example, thebeading portion 180 in the inner surface of the battery housing 171. Thehousing coupling portions 176 c may be coupled, particularly, to thelower surface of the beading portion by laser welding. The welding maybe replaced with ultrasonic welding, spot welding, or the like. Bycoupling the plurality of housing coupling portions 176 c on the beadingportion 180 by welding in this way, the current path is dispersedradially, thereby limiting the resistance level of the cylindricalbattery 200 to about 4 milliohms or less. In addition, as the lowersurface of the beading portion 180 has a shape extending in a directionapproximately parallel to the upper surface of the battery housing 171,namely in a direction approximately perpendicular to the sidewall of thebattery housing 171, and the housing coupling portion 176 c also has ashape extending in the same direction, namely in the radial directionand the circumferential direction, the housing coupling portion 176 cmay be stably in contact with the beading portion 180. In addition, asthe housing coupling portion 176 c is stably in contact with the flatportion of the beading portion 180, the two components may be weldedsmoothly, thereby improving the coupling force between the twocomponents and minimizing the increase in resistance at the couplingportion.

The housing coupling portion 176 c may include a contact portion 176 ecoupled onto the inner surface of the battery housing 171 and aconnection portion 176 f for connecting the support portion 176 a andthe contact portion 176 e.

The contact portion 176 e is coupled onto the inner surface of thebattery housing 171. In the case where the beading portion 180 is formedon the battery housing 171, the contact portion 176 e may be coupledonto the beading portion 180 as described above. More specifically, thecontact portion 176 e may be electrically coupled to the flat portionformed at the lower surface of the beading portion 180 formed on thebattery housing 171, and may be interposed between the lower surface ofthe beading portion 180 and the first gasket 178 b. In this case, forstable contact and coupling, the contact portion 176 e may have a shapeextending on the beading portion 180 by a predetermined length along thecircumferential direction of the battery housing 171.

The connection portion 176 f may be bent at an obtuse angle. The bendingpoint may be higher than the intermediate point of the connectionportion 176 f. When the connection portion 176 f is bent, the contactportion 176 e may be stably supported on the flat surface of the beadingportion 180. The connection portion 176 f may be divided into a lowerportion and an upper portion based on the bending point, and the lengthof the lower portion may be greater than that of the upper portion. Inaddition, the inclination angle with respect to the surface of thesupport portion 176 a may be greater at the lower portion of the bendingpoint rather than at the upper portion. If the connection portion 176 fis bent, the connection portion 176 f may buffer the pressure (force)applied in the vertical direction of the battery housing 171. Forexample, if a pressure is transmitted to the contact portion 176 e inthe sizing process for the battery housing so that the contact portion176 e moves vertically toward the support portion 176 b, the bendingpoint of the connection portion 176 f may move upward to deform theshape of the connection portion 176, thereby buffering the stress.

Meanwhile, the maximum distance from the center of the second currentcollector 176 to the end of the second uncoated portion coupling portion176 b along the radial direction of the electrode assembly 110 ispreferably equal to or smaller than the inner diameter of the batteryhousing 171 in a region where the beading portion 180 is formed, namelythe minimum inner diameter of the battery housing 171. This is toprevent the end of the second uncoated portion coupling portion 176 bfrom pressing the edge of the electrode assembly 110 during the sizingprocess for compressing the battery housing 171 along the heightdirection.

The second uncoated portion coupling portion 176 b includes a hole 176g. The hole 176 g may be used as a passage through which the electrolytemay move. The welding pattern 176 h formed by welding between the seconduncoated portion coupling portion 176 b and the bending surface region Fmay have a structure to extend along the radial direction of theelectrode assembly 110. The welding pattern 176 h may be a line patternor a dot array pattern.

The welding pattern 176 h corresponds to the welding region. Therefore,the welding pattern 176 h preferably overlaps with the overlapping layernumber uniform region b1 of the bending surface region F by 50% or more.The welding pattern 176 h that does not overlap with the overlappinglayer number uniform region b1 may overlap with the overlapping layernumber decreasing region b2. The entire welding pattern 176 h mayoverlap with the overlapping layer number uniform region b1 of thebending surface region F. In the bending surface region F above theregion where the welding pattern 176 h is formed, the number ofoverlapping layers of segments is preferably 10 or more in theoverlapping layer number uniform region b1 and, optionally, theoverlapping layer number decreasing region b2.

The diameters of the first current collector 144 and the second currentcollector 176 described above are different from each other. Thediameter is an outer periphery diameter of the contact area between thebending surface region F and the current collector. The diameter isdefined as a maximum value among distances between two points where astraight line passing through the center of the core C of the electrodeassembly meets the boundary of the contact area. Since the secondcurrent collector 176 is located inside the beading portion 180, thediameter of the second current collector 176 is smaller than thediameter of the first current collector 144. Also, the length of thewelding pattern 144 f of the first current collector 144 is longer thanthe length of the welding pattern 176 h of the second current collector176. Preferably, the welding pattern 144 f and the welding pattern 176 hmay extend from substantially the same point toward the outercircumference with respect to the center of the core C.

The cylindrical battery 170, 180, 200, 220 according to an embodiment ofthe present disclosure have an advantage in that electrical connectioncan be performed at the upper portion thereof.

FIG. 28 is a top plan view illustrating a state in which a plurality ofcylindrical batteries are electrically connected, and FIG. 29 is apartially enlarged view of FIG. 28 . The cylindrical battery 200 may bereplaced with the cylindrical battery 170, 180, 220 having a differentstructure.

Referring to FIGS. 28 and 29 , a plurality of cylindrical batteries 200may be connected in series and in parallel at an upper portion of thecylindrical batteries 200 using a bus bar 210. The number of cylindricalbatteries 200 may be increased or decreased in consideration of thecapacity of the battery pack.

In each cylindrical battery 200, the terminal 172 may have a positivepolarity, and the flat surface 171 a around the terminal 172 of thebattery housing 171 may have a negative polarity, or vice versa.

Preferably, the plurality of cylindrical batteries 200 may be arrangedin a plurality of columns and rows. Columns are provided in an upper anda lower direction on the drawing, and rows are provided in a left andright direction on the drawing. In addition, in order to maximize spaceefficiency, the cylindrical batteries 200 may be arranged in a closestpacking structure. The closest packing structure is formed when anequilateral triangle is formed by connecting the centers of theterminals 172 exposed out of the battery housing 171 to each other.Preferably, the bus bar 210 connects the cylindrical batteries 200arranged in the same column in parallel to each other, and connects thecylindrical batteries 200 arranged in two neighboring columns in serieswith each other.

Preferably, the bus bar 210 may include a body portion 211, a pluralityof first bus bar terminals 212 and a plurality of second bus barterminals 213 for serial and parallel connection.

The body portion 211 may extend along the column of the cylindricalbattery 200 between neighboring terminals 172. Alternatively, the bodyportion 211 may extend along the row of the cylindrical batteries 1, andthe body portion 211 may be regularly bent like a zigzag shape.

The plurality of first bus bar terminals 212 may extend from one side ofthe body portion and may be electrically coupled to the terminal 172 ofthe cylindrical battery 200 located at one side. The electricalconnection between the first bus bar terminal 212 and the terminal 172may be achieved by laser welding, ultrasonic welding, or the like.

The plurality of second bus bar terminals 213 may extend from the otherside of the body portion 211 and may be electrically coupled to the flatsurface 171 a around the terminal located at the other side. Theelectrical coupling between the second bus bar terminal 213 and the flatsurface 171 a may be performed by laser welding, ultrasonic welding, orthe like.

Preferably, the body portion 211, the plurality of first bus barterminals 212 and the plurality of second bus bar terminals 213 may bemade of one conductive metal plate. The metal plate may be, for example,an aluminum plate or a copper plate, but the present disclosure is notlimited thereto. In a modified example, the body portion 211, theplurality of first bus bar terminals 212 and the second bus barterminals 213 may be manufactured as separate pieces and then coupled toeach other by welding or the like.

The cylindrical battery 200 of the present disclosure as described abovehas a structure in which resistance is minimized by enlarging thewelding area by means of the bending surface region F, multiplexingcurrent paths by means of the second current collector 176, minimizing acurrent path length, or the like. The AC resistance of the cylindricalbattery 200 measured through a resistance meter between the positiveelectrode and the negative electrode, namely between the terminal 172and the flat surface 171 a around the terminal 172, may be about 4milliohms or below suitable, but greater than 0 milliohms, such as 0.01milliohms, for fast charging.

In the cylindrical battery 200 according to the present disclosure,since the terminal 172 having a positive polarity and the flat surface171 a having a negative polarity are located in the same direction, itis easy to electrically connect the cylindrical batteries 200 using thebus bar 210

In addition, since the terminal 172 of the cylindrical battery 200 andthe flat surface 171 a around the terminal 172 have a large area, thecoupling area of the bus bar 210 may be sufficiently secured tosufficiently reduce the resistance of the battery pack including thecylindrical battery 200.

In addition, since electrical wiring can be performed at the upperportion of the cylindrical battery 200, there is an advantage in thatthe energy density per unit volume of a battery module/pack may bemaximized.

The cylindrical battery according to the above embodiments(modifications) may be used to manufacture a battery pack.

FIG. 30 is a diagram schematically showing a battery pack according toan embodiment of the present disclosure.

Referring to FIG. 30 , a battery pack 300 according to an embodiment ofthe present disclosure includes an aggregate in which cylindricalbatteries 301 are electrically connected, and a pack housing 302 foraccommodating the aggregate. The cylindrical battery 301 may be any oneof the batteries according to the above embodiments (modifications). Inthe drawing, components such as a bus bar, a cooling unit, and anexternal terminal for electrical connection of the cylindrical batteries301 are not depicted for convenience of illustration.

The battery pack 300 may be mounted to a vehicle. The vehicle may be,for example, an electric vehicle, a hybrid electric vehicle, or aplug-in hybrid vehicle. The vehicle includes a four-wheeled vehicle or atwo-wheeled vehicle.

FIG. 31 is a diagram schematically showing a vehicle including thebattery pack 300 of FIG. 30 according to an embodiment of the presentdisclosure.

Referring to FIG. 31 , a vehicle V according to an embodiment of thepresent disclosure includes the battery pack 300 according to anembodiment of the present disclosure. The vehicle V operates byreceiving power from the battery pack 300 according to an embodiment ofthe present disclosure.

According to the present disclosure, since the uncoated portionsthemselves protruding from the upper and lower portions of the electrodeassembly are used as electrode tabs, it is possible to reduce theinternal resistance of the battery and increase the energy density.

According to another embodiment of the present disclosure, since thestructure of the uncoated portion of the electrode assembly is improvedso that the electrode assembly does not interfere with the innercircumference of the battery in the process of forming the beadingportion of the battery housing, it is possible to prevent a shortcircuit in the cylindrical battery caused by partial deformation of theelectrode assembly.

According to still another embodiment of the present disclosure, sincethe structure of the uncoated portion of the electrode assembly isimproved, it is possible to prevent the uncoated portion from being tornwhen the uncoated portion is bent, and the number of overlapping layersof the uncoated portions is sufficiently increased to improve weldingstrength of the current collector.

According to still another embodiment of the present disclosure, it ispossible to improve physical properties of a region where the currentcollector is welded, by applying a segment structure to the uncoatedportion of the electrode and optimizing the dimensions (width, height,separation pitch) of the segments to sufficiently increase the number ofoverlapping layers of the segments in an area used as a welding targetregion.

According to still another embodiment of the present disclosure, it ispossible to provide an electrode assembly with improved energy densityand reduced resistance by applying a structure in which a currentcollector is welded over a large area to a bending surface region formedby bending the segments.

According to still another embodiment of the present disclosure, it ispossible to provide a cylindrical battery including an improved designso as to perform electrical wiring at an upper portion thereof.

According to still another embodiment of the present disclosure, sincethe structure of the uncoated portion adjacent to the core of theelectrode assembly is improved, it is possible to prevent the cavity inthe core of the electrode assembly from being blocked when the uncoatedportion is bent. Thus, the electrolyte injection process and the processof welding the battery housing (or, the terminal) with the currentcollector may be carried out easily.

According to still another embodiment of the present disclosure, it ispossible to provide a cylindrical battery having a structure that has alow internal resistance, prevents internal short circuit and improveswelding strength between the current collector and the uncoated portion,and a battery pack and a vehicle including the cylindrical battery.

In particular, the present disclosure may provide a cylindrical batteryhaving a diameter to a height ratio of 0.4 or more and a resistance of 4milliohms or less, and a battery pack and a vehicle including the same.

The present disclosure has been described in detail. However, it shouldbe understood that the detailed description and specific examples, whileindicating embodiments of the disclosure, are given by way ofillustration only, since various changes and modifications within thescope of the disclosure will become apparent to those skilled in the artfrom this detailed description.

What is claimed is:
 1. An electrode assembly comprising: a firstelectrode; a second electrode; and a separator between the firstelectrode and the second electrode, the first electrode, the secondelectrode, and the separator wound about an axis defining a core and anouter circumference of the electrode assembly, wherein the firstelectrode has a pair of first sides and a pair of second sides extendingbetween the pair of first sides, a first portion extending between thepair of first sides, and a second portion extending between the pair offirst sides, wherein the first portion is coated with an active materialalong a winding direction, and at least a part of the second portionincludes an electrode tab, wherein the second portion includes a firstpart including an innermost winding turn adjacent to the core of theelectrode assembly, a second part including an outermost winding turnadjacent to the outer circumference of the electrode assembly, and athird part between the first part and the second part, and wherein thefirst part or the second part has a smaller height than the third partin a direction of the axis and the first part does not include a segmentthat is independently bendable.
 2. The electrode assembly according toclaim 1, wherein the third part is bent along a radial direction of theelectrode assembly to define the electrode tab, or wherein the secondpart and the third part are bent along the radial direction of theelectrode assembly to define the electrode tab.
 3. The electrodeassembly according to claim 1, wherein at least a partial region of thethird part is divided into a plurality of segments that areindependently bendable and each of the plurality of segments has ageometric shape in which one or more straight lines, one or more curves,or a combination thereof are connected.
 4. The electrode assemblyaccording to claim 3, wherein the plurality of segments have a lowerinternal angle that increases individually or in groups in one directionparallel to the winding direction.
 5. The electrode assembly accordingto claim 3, wherein each of the plurality of segments has a geometricshape with a width that gradually decreases from a lower portion to anupper portion, and a lower internal angle (θ) of a segment located in awinding turn having a radius r based on the core of the electrodeassembly falls within an angle range of the following formula:${\cos^{- 1}( \frac{0.5*D}{r} )} \leq \theta \leq {\tan^{- 1}( \frac{2*H*\tan\theta_{refer}}{{2*H} - {p*\tan\theta_{refer}}} )}$wherein D is a width of the segment in the winding direction, r is aradius of the winding turn including the segment, H is a height of thesegment, and p is a separation pitch of the segment.
 6. The electrodeassembly according to claim 3, wherein the plurality of segments have acut groove between segments adjacent to each other along the windingdirection, and a lower portion of the cut groove includes a bottomportion and a round portion connecting both ends of the bottom portionto sides of the segments adjacent to each other.
 7. The electrodeassembly according to claim 6, wherein the bottom portion of the cutgroove is flat.
 8. The electrode assembly according to claim 6, whereinthe bottom portion of the cut groove is spaced apart from the firstportion by a predetermined distance.
 9. The electrode assembly accordingto claim 6, wherein an insulating coating layer is formed at a boundarybetween the first portion and a region of the second portion provided ina section where the bottom portion of the cut groove and the firstportion are separated, and wherein the second electrode includes a thirdportion coated with an active material along the winding direction, andan end of the third portion is located between an upper end and a lowerend of the insulating coating layer in the direction of the axis. 10.The electrode assembly according to claim 3, wherein in each of theplurality of segments, a width of the segment in the winding directionD(r) satisfies the following formula:1≤D(r)≤(2*π*r/360°)*45°, wherein r is a radius of a winding turnincluding the segment based on a core center of the electrode assembly.11. The electrode assembly according to claim 10, wherein in each of theplurality of segments, as the radius r of the winding turn where thesegment is located based on the core center of the electrode assemblyincreases, the width D(r) in the winding direction increases ordecreases gradually or stepwise.
 12. The electrode assembly according toclaim 3, wherein the core of the electrode assembly is not covered by abent portion of the plurality of the segment by at least 90% or more ofa diameter thereof.
 13. The electrode assembly according to claim 3,wherein the electrode assembly includes a segment skip region having nosegment, a height variable region where segments have variable heights,and a height uniform region where segments have a substantially uniformheight in order along a radial direction, based on a cross section alongthe direction of the axis, and the plurality of segments are disposed inthe height variable region and the height uniform region and bent alongthe radial direction of the electrode assembly forming a bending surfaceregion.
 14. The electrode assembly according to claim 3, wherein widthsof the plurality of segments in the winding direction or heights thereofin the direction of the axis, or both increase gradually or stepwisealong one direction parallel to the winding direction.
 15. The electrodeassembly according to claim 3, wherein the plurality of segments form aplurality of segment groups along one direction parallel to the windingdirection of the electrode assembly, and segments belonging to the samesegment group are substantially the same as each other in terms of awidth in the winding direction and a height in the direction of theaxis.
 16. The electrode assembly according to claim 15, wherein widthsof the segments belonging to the same segment group in the windingdirection or heights thereof in the direction of the axis, or bothincrease stepwise along one direction parallel to the winding directionof the electrode assembly.
 17. The electrode assembly according to claim3, wherein the electrode assembly includes a bending surface regionformed by bending the plurality of segments along a radial direction ofthe electrode assembly, and wherein, when the number of segments meetinga virtual line parallel to the direction of the axis at any radiallocation of the bending surface region based on a core center of theelectrode assembly is defined as the number of overlapping layers ofsegments at the corresponding radial location, the bending surfaceregion includes an overlapping layer number uniform region in which thenumber of overlapping layers of segments is substantially uniform fromthe core toward the outer circumference and an overlapping layer numberdecreasing region located adjacent to the overlapping layer numberuniform region and the number of overlapping layers of segments in theoverlapping layer number decreasing region gradually decreases towardthe outer circumference, and wherein, in the overlapping layer numberuniform region, the number of overlapping layers of the segments is 10to
 35. 18. The electrode assembly according to claim 3, wherein theelectrode assembly includes a bending surface region formed by bendingthe plurality of segments along a radial direction of the electrodeassembly, and wherein, when the number of segments meeting a virtualline parallel to the direction of the axis at any radial location of thebending surface region based on a core center of the electrode assemblyis defined as the number of overlapping layers of segments at thecorresponding radial location, the bending surface region includes anoverlapping layer number uniform region in which the number ofoverlapping layers of segments is substantially uniform from the coretoward the outer circumference and an overlapping layer numberdecreasing region located adjacent to the overlapping layer numberuniform region and the number of overlapping layers of segments in theoverlapping layer number decreasing region gradually decreases towardthe outer circumference, wherein a ratio of a radial length of theoverlapping layer number uniform region to a radial length of theoverlapping layer number uniform region and the overlapping layer numberdecreasing region is 30% to 85%, and wherein the first electrode is apositive electrode, and in the overlapping layer number uniform region,an overlapping thickness of segments is between 100 μm and 875 μm, orwherein the first electrode is a negative electrode, and in theoverlapping layer number uniform region, an overlapping thickness ofsegments is between 50 μm and 700 μm.
 19. The electrode assemblyaccording to claim 18, further comprising: a current collector welded tothe bending surface region, wherein, in the radial direction of theelectrode assembly, a welding region of the current collector overlapswith the overlapping layer number uniform region by at least 50%, andwherein a welding strength of the current collector to the weldingregion is at least 2 kgf/cm2 or more.
 20. The electrode assemblyaccording to claim 1, wherein the third part is divided into a pluralityof regions having different heights along one direction parallel to thewinding direction, and the height of the third part in the plurality ofregions increases gradually or stepwise along one direction parallel tothe winding direction.
 21. The electrode assembly according to claim 1,wherein the third part includes a plurality of segment skip regionsalong the one direction parallel to the winding direction, wherein theplurality of segment skip regions have widths gradually increasing ordecreasing along the one direction parallel to the winding direction,and wherein the plurality of segments are located in at least twosectoral regions or polygonal regions disposed in a circumferentialdirection based on a core center of the electrode assembly.
 22. Abattery, comprising: an electrode assembly including a first electrode,a second electrode, and a separator between the first electrode and thesecond electrode, the first electrode, the second electrode, and theseparator wound about an axis defining a core and an outercircumference, wherein the first electrode has a pair of first sides anda pair of second sides extending between the pair of first sides, afirst portion extending between the pair of first sides, and a secondportion extending between the pair of first sides, wherein the firstportion is coated with an active material along a winding direction, atleast a part of the second portion includes an electrode tab, the secondportion includes a first part including an innermost winding turnadjacent to the core of the electrode assembly, a second part includingan outermost winding turn adjacent to the outer circumference of theelectrode assembly, and a third part between the first part and thesecond part, the first part or the second part has a smaller height thanthe third part in the direction of the axis, and the first part thefirst part does not include a segment that is independently bendable; abattery housing including a first end with a first opening and a secondend opposite thereto, wherein the electrode assembly is accommodated ina space between the first end and the second end, and the batteryhousing is electrically connected to one of the first electrode or thesecond electrode to have a first polarity; a sealing body sealing thefirst opening at the first end of the battery housing; and a terminalelectrically connected to the other of the first electrode or the secondelectrode to have a second polarity and having a surface exposed outsidethe battery housing.
 23. The battery according to claim 22, wherein thesecond part has a smaller height than the third part in the direction ofthe axis, wherein the battery housing includes a beading portionpress-fitted inward at a region adjacent to the first opening at thefirst end, and wherein a press-in depth D1 of the beading portion and adistance D2 from an inner circumference of the battery housing to aboundary between the second part and the third part satisfy a formulaD1≤D2.
 24. The battery according to claim 22, further comprising: afirst current collector electrically connected to the second portion,wherein the terminal is a rivet terminal installed in a hole formed inthe second end of the battery housing to be insulated therefrom andelectrically connected to the first current collector to have the secondpolarity.
 25. The battery according to claim 24, further comprising: aninsulator between an inner surface of the bottom portion of the batteryhousing and an upper surface of the first current collector toelectrically insulate the inner surface of the bottom portion of thebattery housing and the first current collector, wherein the insulatorhas a thickness corresponding to a distance between the inner surface ofthe bottom portion of the battery housing and the upper surface of thefirst current collector and is in contact with the inner surface of thebottom portion of the battery housing and the upper surface of the firstcurrent collector.
 26. The battery according to claim 25, wherein theterminal includes a flat portion at a lower end thereof, wherein theinsulator has an opening for exposing the flat portion, and wherein theflat portion is welded to the first current collector through theopening.
 27. The battery according to claim 22, wherein the secondelectrode has a pair of third sides and a pair of fourth sides extendingbetween the pair of third sides, a third portion extending between thepair of third sides, and a fourth portion extending between the pair ofthird sides, wherein the third portion is coated with an active materialalong the winding direction, wherein the second electrode has the firstpolarity, and at least a part of the fourth portion includes anelectrode tab, and wherein the battery further includes a second currentcollector electrically connected to the fourth portion and having anedge at least partially coupled to a sidewall of the battery housing.28. The battery according to claim 27, wherein the battery housingincludes a beading portion press-fitted inward at an inner wall adjacentto the first opening at the first end, and the edge of the secondcurrent collector is electrically connected to the beading portion. 29.The battery according to claim 28, wherein the battery includes a caphaving an edge supported by the beading portion and having no polarity,a gasket between the edge of the cap and the first opening at the firstend of the battery housing, and a crimping portion bent and extendedinto the first opening of the battery housing and surrounding and fixingthe edge of the cap together with the gasket, and wherein the edge ofthe second current collector is fixed between the beading portion andthe gasket by the crimping portion.
 30. A method of producing a battery,the method comprising: forming an electrode assembly having a firstelectrode, a second electrode and a separator between the firstelectrode and the second electrode, wherein the first electrode, thesecond electrode, and the separator are wound about an axis defining acore and a circumferential surface of the electrode assembly, whereinthe first electrode has a pair of first sides and a pair of second sidesextending between the pair of first sides, a first portion extendingbetween the pair of first sides, and a second portion extending betweenthe pair of first sides, wherein the first portion is coated with anactive material along a winding direction, wherein at least a part ofthe second portion includes an electrode tab, wherein the second portionincludes a first part including an innermost winding turn adjacent tothe core of the electrode assembly, a second part including an outermostwinding turn adjacent to the outer circumference of the electrodeassembly, and a third part between the first part and the second part,the first part or the second part has a smaller height than the thirdpart in the direction of the axis, and the first part the first partdoes not include a segment that is independently bendable; forming abattery housing having a first end with a first opening and a second endopposite the first end, the battery housing accommodating the electrodeassembly in a space between the first end and the second end andelectrically connected to one of the first electrode or the secondelectrode to have a first polarity; forming a sealing body sealing thefirst opening at the first end of the battery housing; and forming aterminal electrically connected to the other of the first electrode orthe second electrode to have a second polarity and having a surfaceexposed outside the battery housing.